OK, so thank you very much for the introduction.
Thank you very much for the invitation.
And indeed, I'm talking about things
which I've been doing in my former life.
And I was affiliated with the Max Planck Institute
for Nuclear Physics and also with the Center for Free
Electron Laser Science here at Hamburg,
where I was running the Max Planck Advanced Study Group.
Now, I'm going to talk about ultrafast dynamics,
pump probe experiments at FELs.
And you might ask yourself, why should we do that?
Because we had decades of pump probe experiments with lasers.
And in my first few slides, I would
like to motivate this a little bit.
Namely, you all know what a pump probe experiment is.
You have a potential energy surface in the ground state,
say, and you pump a wave packet up in an excited state.
The wave packet evolves.
And at some point, you probe it.
And usually, you have an optical laser with a certain frequency.
And you can only probe this when the energy difference here
between the two potential energy surfaces
fits your laser intensity.
So you can only probe it at that part.
And you need to know, sometimes,
you need to have spectroscopic knowledge about the system
which you are probing, because you would like
to know where you are probing.
Now, with a free electron laser, you have higher photon energies.
And with your probe photon, you could easily,
because this arrow is longer, you
can easily go into the continuum always.
You can always ionize the system.
And this is an advantage, because now you
don't need spectroscopic knowledge.
It's just ionized.
You go along the whole reaction, the entire reaction coordinate.
You can monitor your system, so to say,
independent where it is.
Furthermore, very often, you come to a repulsive surface
here.
And this just projects the wave packet from here
into the continuum, into momentum space.
And you get direct information about the wave packet.
You can at least get direct information
about the wave packet.
Moreover, for theoreticians, very important,
you could also do that ionization
by multi-photon ionization.
But this is difficult, theoretically,
because it's non-perturbative.
Now you have just the single photon
bringing you into the continuum.
And from the theoretical point of view, this is easy to treat.
It's just a perturbative probe.
Now finally, you get an electron out here.
And if you measure this electron,
you get direct information about the electronic state, which
was involved at the time you ionize here.
And even moreover, this electron goes out
of this many-center potential and is
being scattered on this potential.
And by that, you get information
about the electronic density at that time.
And there are beautiful experiments.
I will possibly come back to that.
There are beautiful experiments, non-time dependent
experiments, where you have an aligned molecule.
And you look for the electron emission
in space, in three-dimensional space.
This was essentially your question.
I will come to that back.
And this we would like to see as a function of time,
how these electrons go out of this evolving
many-dimensional electronic density distribution.
And even more importantly, I think,
if this photoelectron is very high energetic,
it's being diffracted on its way out in a way
that you get direct information, possibly direct information
about the nuclei.
So this is the benzene ring.
This is the calculation.
So you might get direct information
how the nuclei move as a function of time.
And even more, you can not only look on the scattered
electrons, but in the free electron laser,
you have photons being scattered, a lot of photons
at a given time.
And you might get coherent images
of big molecules, of proteins or so, as a function of time,
and get information.
You pump a big system, and you get structural.
And you might get structural information
about a big protein, for instance,
when it executes its function.
And I will come at the end of my talk if I have enough time.
I will show you some examples on that.
So in my opinion, there is a kind of a new era coming up
in pump probe experiments, and dynamic experiments
on small and large molecules with these free electron
lasers.
And this is why we started that.
I'm talking about two different topics, essentially,
different wavelengths in the VUV regime.
And these experiments we have done here
at FLESH in Hamburg, and also some of them in Japan,
where we have another free electron laser for low energies.
And then, if I have time enough, I show you a little bit
what are the first steps towards x-rays, time-dependent x-rays.
And this we have done at the linear coherent light source
at Stanford.
First of all, I would like to show you
a little bit about the experiment.
How do we do the experiment?
And how do we characterize the pulses, actually?
So this is the experimental hole here at FLESH.
And what comes out here is photon energies
between 20 and 400 eV.
A lot of photons, 10 to the 13 photons in very short time,
7 to 50 femtoseconds.
And depending on your focusing conditions,
you get a lot of intensity, 10 to the 16 watts per square
centimeters.
And the repetition rate, we're just
doing an experiment right now.
You have a micro pulse of 10 hertz.
And there are micro bunches in these 10 hertz pulses.
So effectively, we can now do an experiment at 1 kilohertz.
And this is very important, these properties,
that we have short pulses, that we have high intensity.
Because if you pump a molecule, we
have to make sure with a probe pulse
that we really can talk to this molecule.
We need quite some intensity, photon intensity,
to have a high probability.
And the high repetition rate, this all makes these sources,
I think, also from their properties,
very ideal to do these kind of pump probe experiments.
Now, we have to characterize the pulse.
I don't go into any details of the free electron laser.
But what is shown here, and you can hardly read it,
this is a wavelength of about 13 nanometers or so.
And this is pulse by pulse.
You see these wavelength distributions.
And it's shumping.
Because the free electron laser process
produces the pulse out of the noise.
And depending on how the electron bunch was,
you get different light out of that.
And you see these different spikes here.
And if you Fourier transform that in the time domain,
you will get the same picture in the time domain.
So it's not very well defined.
Finally, it's well behaved.
If you sum up everything, you get the red curve.
Nevertheless, this doesn't help you in the pump probe
experiment, because you would like to see what's going on.
You have to characterize that.
And even worse, the structure of these pulses
depend extremely sensitively on the setting
of the whole machine.
So nobody knows when you start an experiment,
nobody knows actually what you start with.
So you have to characterize that.
And so how to do that?
You can do an autocorrelation experiment.
And this is what we always do when we start such a time
dependent measurement.
What do you do?
You split the pulse in two parts.
And then you have a nonlinear detector,
which might be an atom or a molecule.
And you measure this n-th order autocorrelation signal.
And I just indicate how this works in principle.
So say you have a pulse in the time domain, which
looks like that, has two spikes.
This is very typical.
And you split them into identical replica.
And then you delay one versus the other.
And look on a nonlinear signal.
The nonlinear signal is coming up here.
And you now overlay that.
And then you see it's going up.
And it's going essentially very high up
when you are at the point where it's very full overlap.
So you get, in principle, information
about something like the full width half maximum here,
but also on the spikes.
And those are related to the coherence lengths of the FER.
Now, what did we do?
What did we use as a nonlinear signal?
We just used two-photon absorption of helium.
So if you have 20 EV photon energy,
you cannot ionize by one photon, obviously,
because you have a binding energy of 24.
So you need two photons.
And this depends quadratically.
The intensity, the yield of helium plus ions you get,
depends quadratically on the intensity.
And this is shown here.
We measure that.
We verify that.
So this is the intensity.
Here's the ion yield, just the number of ions here.
And you see it's quadratically.
So we have our second order process.
And we just need now, as a function of the delay,
look on the signal here on the helium plus ions.
So we did these experiments here, but also in Japan.
And if you look into this experimental hall,
here are the beam lines.
So here, the FEL light comes along these lines.
And this here is our experiment, which
we call cold rims or reaction microscope.
And if you look a little bit more detail, this is it.
So you need very good vacuum, as you can see.
And how does it work?
And this was your question, essentially.
So we have a supersonic jet where
we have all kind of gases, which we would like to have.
And then we focus the FEL beam onto the supersonic jet.
And we hit individual atoms or molecules or dimers
or for ICD, like Reinhard Donner is doing that.
And then you have an electric field.
And by this electric field, you can essentially
get all the ions onto one detector.
You measure the time of flight and the heating position.
And they get the vector momentum for all emission
in all space, so to say.
At the same time, you can also look for the electrons.
The electrons have larger energies
because they are lighter.
So you cannot project them easily
by an electric field alone.
So we have an additional magnetic field.
This one here is generated by these Helmholtz coils.
And this forces the electron-inspired trajectories.
And again, by measuring the heating position
and the heating time, you can recalculate the momentum.
So for ICD, for instance, in these experiments,
they have measured in coincidence
two of the ions, two neon ions, and the electrons.
So you get the full information about the full solid angle.
And this is shown here for our process for signal ionization
by two photons.
So this is the angular distribution,
in this case of the ion or of the electron
because it's identical, more or less,
because a photon has nearly no momentum.
And what you can see here, this is in 3D here.
It's cut a little bit.
This is maybe one of your questions.
You don't get those guys who are too fast in this direction.
So it's cut a little bit here at that part.
But you can deal with that.
And you see, that is not a dipolar distribution.
You have another contribution here
because we had two photons.
Delta L is equal to 2.
You start with an S state.
So you have a superposition of S and D.
And depending on the energy.
And so this is also a verification
that we have the right process.
OK, and now with that, we do our pump-robe experiments.
How do we do that?
Now we come in with an unfocused FEL beam
and have a multilayer, split it mirror
at the end of our experiment.
And we focus back onto the supersonic jet.
And now we can move the two halves of the mirror
versus each other and implement a delay.
And this is a big machine here.
This is a mirror.
It took us some years, actually, to get
this running in collaboration with many people,
with Amulf, with FOM, LB&L, and Fraunhofer.
So this is a piece of an art, actually,
because you have to really overlap on a micrometer size
and things like that.
OK, nevertheless, it worked finally.
And this is an experiment which we did in Japan at SCSS
together with Kiyoshi Ueda.
And here you see such an autocorrelation trace.
You see a large part, a longer part,
which is just the envelope of the pulse, 30 femtoseconds,
in this case.
And then you see a smaller part, a shorter part,
on top of it, which is only 7 femtoseconds.
And this is the coherence length of the radiation.
And then we developed a little model.
Thomas V, actually, developed a little model
where, from the general properties of the FEL spectrum
and time properties, we created individual pulses
in the time domain or in the spectrum domain.
Sorry, and this was done by Thomas Pfeiffer here.
So these are the individual pulses.
Many of those, randomly, are generated
by knowing the properties of the FEL radiation.
And then we do, theoretically, the autocorrelation.
And by that, we get the black line here.
So we understand very well what's going on.
So it's very well behaved.
And we know our pulses extremely well now.
And then we can go for an interpretation
of our experiment with this background.
What you also can see, and this puzzle does a while,
is that this little spike on top of this broader distribution
is not at the center.
So we didn't know what that is.
But it turned out that one possible explanation is,
and the accelerator physicists agree,
that the wave front, which is coming in and which is then
finally by our mirror, which is splitted in two halves,
is being splitted.
This might be tilted a little bit.
And then you always have an additional time delay,
so to say, on one part.
And we calculate it out of our measurement,
which there is no other explanation, I think,
that there is really a tilt in the wave front.
So we can really now analyze these FEL pulses quite well
and be very sure of what we have.
And this is actually also done right now in the experiment.
Another interesting thing I will come to that
is that you might hope that you might even
be able to get time resolution in the order of the coherence
lengths, not on the envelope here,
but on the coherence lengths.
And I will come to that also at some point.
So this is a publication, Robert Mozzama and Thomas Pfeiffer,
where the important people here, together
with our Japanese colleagues, Kiyoshi Ueda and others.
OK, there's also another interesting thing.
If you go to x-ray of free electron lasers,
and this is the power radiated as a function of meters
in the multilayer, nevertheless, at some point
you get very short pulses with very many spikes.
So this is two femtoseconds for an x-ray laser.
This was VUV, which I had before.
And the spikes here are only 2,300 other seconds long.
So I'm very much convinced that by these technologies
you can get x-ray, other second time-resolved experiments
in the future.
And you will see that in the future.
Now, we did a proof of principal experiments.
We have to make sure that things are correct.
And we started with a very simple system, namely with D2.
This is a ground state of D2.
This is a ground state of the ion.
Then you have a lot of excited state,
and not all of them are plotted here.
Interesting are these doubly excited states.
And this is something which we would
like to explore in the future, because these doubly excited
states decay very quickly in the femtosecond time machine.
In the same time machine, the nuclei are moving.
So you can explore things beyond Born-Oppenheimer,
so to say, because electronic motion and nuclear motion
somehow is on the same time scale.
Now, and here you are on this Coulomb repulsive surface
where you ionize two of the electrons.
Now, theoretically, as I said, this is interesting and also
challenging if you would like to make a full calculation,
because you have two photons, two electrons, two nuclei,
and you have to treat all the motions, so to say,
in order to make it correct.
OK, now we do our pump-robe experiment with 38 EV photons.
So with the first photon, we go up to here,
and we thought we go into this doubly excited state.
But nevertheless, we did a proof of principle experiments
finally only, because then you can
see that you populate with 95% the ground state
of the molecule here by this photon.
And now a wave packet, as I showed you at the beginning,
starts to move back and forth.
Here it goes in this direction, and so on.
And now we come to the second photon.
And if it comes at the inner turning point,
then you have removed two electrons from the system.
So your ions explode.
You get a Coulomb explosion.
And the kinetic energy release is proportional to the distance
where you got these very ionized.
So you roll down, so to say, this Coulomb wall here.
And this is what you measure.
So this is the kinetic energy release.
And you see a high energy part.
This is when you really find the molecule here
at closer distances.
And if the molecule went out somewhere here after some delay
and you ionize then, then the kinetic energy release
is obviously smaller, because they are further apart
from each other, and you get this part.
And this we can now do as a function of time.
So this is a time trace.
And then you see not so clearly.
And I'll show you why.
But nevertheless, you see these kind of oscillations.
And you can trace it out.
You can just project this part out.
And then you see very clearly that we also
have clear oscillations.
And this was one of the surprises.
We had structures in there which are much shorter
than the envelope of our pulse, which was 40 femtoseconds
at this time.
So this is only 7 femtoseconds.
And this triggered all these calculations
which I showed you before.
The return time is about 22 femtoseconds.
This is very reasonable.
And Fernando Martin from Madrid and his group,
he did calculations for us.
And this is his wave packet calculations.
If he had infinite resolution, we
should see something like that.
And this is now also something which
I said at the very beginning.
You can now at any time step, you can see the full wave
packet.
You project the full wave packet from here
into this into momentum space.
And you can really observe the molecule wherever
given time, one of the mechanics,
it can be at any place sometimes with some probability.
Now if you trace this out, it's in quite good and reasonable
agreement with our measurements.
So we are quite confident that we do the right thing.
Now having understood and having measured our pulses,
we applied this method to analyze our data in a new way.
So if you would have pulses which
are 5 femtoseconds short and Fourier transform limited,
then you would measure that.
As a little bit smeared out, if you
have 40 femtosecond pulses, you wouldn't measure anything
because the pulses are too long for these 22 femtoseconds.
If you have our femtosecond noisy pulses with the spikes,
you recover some structure.
And this comes already quite close to what we see here.
And now very interestingly, Thomas Pfeiffer
developed an idea that you can now,
if you have enough statistics in your experiments,
you can Fourier transform this into the frequency regime
and get rid of all the DC part of the frequencies
and then re-transform into the time domain.
And by that, he could essentially
recover all the details of the wave packet motion.
And we have just finished an experiment now
with very good statistics over several weeks.
And I'm hopefully very confident that we can then
do these kind of tricks and get the full wave packet motion
with very high fidelity.
The coherence length finally defines the resolution.
And this has just been accepted in physical review letters.
Now, this was the proof of principle.
And now I show you very briefly, I essentially
omit that because I have only 35 minutes, so it was 40.
You might also profit from other properties in this FEL radiation.
Namely, you could excite highly excited states
because now different from optical lasers,
you have higher frequencies.
And you simply can go to higher states.
And one of the states which was interesting for us
is this doubly ionized N2 states.
They are metastable, all of them.
There are seven of those.
And then you come again with a delayed probe
and you go up to this triple ionization stage.
And by that, you can for the first time
essentially get the information about these states.
And I don't want to go into any detail here.
And don't be confused.
I'm just clicking away now several of my slides.
We have done these experiments and we have traced some of these states here.
We can identify them.
We had a collaboration with Uvutum from Kansas State University.
And he could show or could identify theoretically
what states we have been looking at.
So now comes a series of slides.
Don't be confused.
OK.
Then I would like to briefly tell you another topic
which we have investigated, which I think is on the long run quite
interesting.
We can do many of these investigations.
Again, I'm not being too detailed because I
assume that there is another talk by Ariel Ventel.
And he will talk about that.
I will just show you a little bit and give you an appetizer,
so to say, what you can do with these kind of things.
Isomerization, probably you know, is very important in life.
It's essentially also for biology.
For instance, vision is essentially based on an isomerization process.
So we would like to understand that.
And we try to understand that for a very simple molecule,
the simplest one, which is undergoing isomerization.
And this is acetylene, which is a linear molecule usually.
If you remove one electron by 38V electron photon energy,
you create the cationic state.
But you can also doubly ionize, but we neglect that.
And here you have the ground state of the ion,
of the molecular ion, and the excited state here.
And since more than 30 years, essentially,
this was debated from Burke at singleton radiation.
It was known that this state, this is the interesting one,
and we populate it by about 30% by these 38 EV photons.
It was known that this state decays quite quickly.
It was also known that it does not decay radiatively.
It was also known that it does not just dissociate.
And it was speculated.
There were essentially two theoretical approaches, I think,
that it might non-radiatively decay through very fast
conical intersections, which we had before by lens.
Or there is also a possibility for an isomerization,
where the proton goes to the other side.
And these are the isomeric states,
which are more or less nearly degenerate.
And as you can see, you cannot reach them
from the ground state here.
So the ground state here is stable.
You cannot go there to the isomeric state.
But from here, you could go there.
And this is what we were after.
We wanted to see whether we can find this process here
by having a probe pulse ionizing the system.
Now, how does it work in the experiment?
So we have this linear acetylene molecule.
We remove one electron.
By that, there's some probability
that the proton migrates to the other side
and would like to know what the time scale is of that.
So we come as a function of time with a second photon.
We move from here one other electron.
Then the thing, again, coulomb explodes.
And if we see in coincidence these two fragments, C plus
and CH2 plus, then we are sure that the proton has
migrated to the other side.
And so we can do these coincidences with our machine.
And this is such a coincidence plot.
And you see, most of the intensity here,
don't go into detail, is a symmetric channel.
CH plus, CH plus.
This is most of the intensity.
And this little guy here, this is a channel which we are after.
And now we just need to look on the time dependence
of this intensity here.
And this gives us, then, the migration time, the proton
migration time.
And this is what we measured, something like 50 femtoseconds
plus minus 15 femtoseconds.
And this is published here.
And our theory colleagues did some calculations.
And I don't want to go into any detail.
This is more detailed, whether you include
this non-adiabatic decay through the conical intersection
or not.
And you see, theoretically, there
is some structure on longer timescales even,
and also on shorter timescales.
There might be some structure here, which we don't know,
because the statistic is too bad.
But as I said, we have just now finished
a run with a lot of statistics.
And we hope that we might see these differences here
between including the passage through the conical intersection
or not.
And then we could possibly, just by our experiment here,
looking on the details of the isomerization process,
also get a clue on the decay through the conical
intersections.
I'm quite sure that this should work in principle, at least,
if you have enough statistics.
OK, so then in the last, oh, no, not really.
There are other channels, right, which you measure.
Things like C2 plus and H2 plus, this has different timescales.
So there are a lot of other things to calculate for our theoretical colleagues.
There's a lot of interesting other simple molecules, kind of,
like ring openings, ring closings, and so on.
So they're very basic, I think, dynamical mechanisms or reactions
in small molecules, which we now can explore by these kind of methods.
OK, one more little hint.
Can we really see the protons move around?
And we have been looking on that and looking into our data.
And the idea was that if this proton is moving around at some time,
it might be here.
You just ionize twice with your FeL pulse, which is very strong.
You might with your probe pulse ionize, doubly ionized.
And then you get these kind of fragments.
And then you can look for all the momenta of these particles
and see where the proton was, whether it's closer to here, here, here,
or whatever.
And this we plotted in a kind of a Newton plot.
This is how it's called.
So all the events which we generated, we turn in such a way
that the proton is always going in this direction.
And then we look relative to this direction to the other two guys.
And this is such a blood.
So the proton goes in this direction.
And here is a CH plus.
It's on the opposite, which you would expect.
And then we look also for the C plus.
This goes to the proton here.
And this means this is something like the acetylene configuration,
because these two are close to each other.
Now, as a function of time, you would hope that this guy moves here.
That would be isomerization.
And by that, you can really see the wave packet going around here
and see them move, so to say.
In this first experiment, we just looked on the intensity here.
And we saw, indeed, that it is increasing.
Since we had a bad pulse, the timescale is not completely correct here.
But this experiment we have just done.
And then hopefully, and I'm quite sure that you will see these pictures again,
we can really see them move.
This is shown here.
So this is our experiment.
And these are some first calculations where you really
see kind of moving these protons going around.
And this is only an appetizer for Oriel's talk.
I'm quite sure that he's going to talk about similar things.
Not about that.
OK, good.
So anyhow, you got the idea, right, that you
can, by these multi-coincidences, that you can really trace out
what the timescale is.
And this is not so simple.
And it just not only goes from here to there,
as you might think, as a simplistic experimentalist.
No, it's a wave packet motion.
It's spreading.
It might even go back, and so on and so forth.
And I think there's a lot of interesting dynamics to be explored here.
OK, and with that, I would like to shortly go to the x-rays.
What can you do with the x-rays?
And for that, these are only the first steps now, right?
I mean, we just had these machines now since two years or so,
2009, three years already, two and a half.
And this is difficult experiments, but we made the first steps.
Going to LCLS, to Stanford, this is a big machine.
You need to have a long electron accelerator
to get electrons up to 14 GV. And then you
go through undulators as in a synchrotron
and get your radiation out.
Now, these undulators have to be very long.
In this case, 130 meters in order to get this lacing finally.
And I have no time to go into any detail.
And out comes something very similar, which
I have shown you before for the VUV regime.
But now we have much higher energies, up to 10 kV.
And this is a wavelength of one angstrom.
So if you look for scattered photons,
you should be able to resolve one angstrom, maybe as a function of time,
as I'm going to show to you.
Again, you have a huge number of photons, very short pulses.
People are actually convinced that they can get one femtoseconds and below.
So we can expect that we get x-ray experiments with an x-ray resolution
in the femtosecond and even sub-femtosecond regime.
And we built an experiment now where we not only
looked for the electrons and the ions, which I've showed you before,
but also for the scattered photons.
And this is the machine here.
It was quite some effort and was some money, actually, also involved.
It was five Max Planck institutes and one company.
And this was headed by the Max Planck Advanced Study Group.
We had more than 25 experiments.
It was a very successful end station at LCLS because it was quite general.
Can do a lot of experiments over there.
And many people contributed just to building this experiment,
especially also Lotash Truda and many others, as you can see.
Now, if you look inside this, the FAL beam comes from here.
Here you see only a lot of cables and you don't really learn much.
If you look inside, then you see the FAL beam comes from the left.
Here are all the electrodes for imaging the electrons and the ions.
So the ions are imaged to the upward side.
Here you see a trace of the ions through the rascals.
Electrons are imaged to the downside.
And then in addition now, we can see the photons being
scattered in the forward direction.
We have large CCD cameras, x-ray CCD cameras, which were developed
by the Max Planck Institute, Max Planck Society, an institute in Munich.
One megapixel, very low noise.
You get also frequency information and very fast readout, 200 hertz readout.
So these are really essential for these kind of experiments.
Now we made the whole experiment such that you can really implement atoms,
molecules, clusters, viruses, anything, proteins.
So depending on your target system you have.
And we could also feed in lasers for pumping the system, for
initiating some dynamics, and also for aligning molecules, for instance.
Okay, and I would like to show you one example.
There are many of those.
And one time dependent, first time dependent example.
Where people, and this was suggested by Peter Gaffromme.
These are large collaborations actually.
We come from the, I'm not a biophysicist, obviously.
But these people know what they want to look for in biology.
And in this case, it was on photosystem I and II in chlorophyll.
And as you all know, without photosynthesis, we wouldn't be here.
So this is a very, very important reaction,
which nature invented a very long time ago.
And how does it happen?
So in the chlorophyll, there are these kind of membranes here,
tilakite membranes.
And in these membranes, embedded, they are large molecular complexes.
Photosystem I, photosystem II.
They are so-called transmembrane proteins.
And they absorb the photons, and finally transfer CO2 into sugar.
This is what finally happens.
And these are the most abundant light harvesting systems in the world.
And what you would like to know now is, and these people would like to know,
is if you absorb a photon, what are the structural changes as a function of time?
How does a molecule do its job, so to say?
And so you look on that, and something is known already by other methods.
Namely, that the photon is absorbed somewhere in here.
And actually, I must admit, I don't know all the details on that as well.
But somewhere it's absorbed in here.
And then this electron is transferred over 60 angstrom
to this ferrodoxin complex here.
So the charge is separated, and the ferrodoxin is reduced.
And after this reduction, this guy goes away and reduces NID P plus
2NADP, and this finally is the reaction.
Now, there are many time steps, obviously, in here.
But one time step which we were sensitive on is that if this guy goes away here,
essentially this thing is not stable anymore, at least in the environment,
which you could produce for the experiment.
So this is kind of dissolving, and the question was on what time scale.
Now, how do you do the experiment?
Now, in our chamber, we had such a nozzle here,
where there's a water jet, a very thin water jet, 40 microns thick.
And in this water jet, if you look in there,
there are little nano crystals of this photosystem I.
You can crystallize it to nano crystals.
There are 200 times up to 1 micron, 200 nanometer up to 1 micron.
So accidentally, they're flying by here.
And once in a while, they are hit by the x-rays.
And then you get scattering.
You get break peaks, because you have a crystal, so to say.
And from that, you get the structure, essentially.
Now, in this case, we want to pump the system also.
And since you have some velocity here, and the typical time scale which
people thought are important is in the order of 10 microseconds or so,
we had to pump the system a little bit upstream, so to say,
that the probe would just get the right signal here, the right molecule here.
And then you look on our detectors, which are as big as my two hands.
You look on the diffraction as a function of time.
These are several pictures now of these Bragg deflections on these CCDs.
They are two-fold.
This is the upper part, the lower part.
And you see a lot of Bragg peaks here.
And this was without time resolution.
And since you have 100 hertz radiation coming in,
and you go all the time with new molecules or little crystals coming in,
you get a lot of scattering.
And altogether, we got, at this first experiment,
something like 3 million patterns.
And these could be, as the crystallography people say, could be indexed.
You get the orientation, so to say.
And finally, you get a three-dimensional electron density distribution.
This is what you want to have.
At this case, because we had only 2kV photon energies,
the resolution was not so good.
Something like 20 angstrom.
And now people have made a lot of progress.
And they can go down into the two-angstrom regime or something like that.
And this was an early paper, also again from Peter Frommer,
but mainly also from Henry Chapman from the Center for Free Electron Laser
Science.
And this is actually opening a new field, even without time dependence,
because you can now examine the structure of small brought in crystals,
which you could not examine before.
Now, however, we can also look for the time dependence.
And this is now a similar picture after 5 microseconds.
This is after 10 microseconds.
And here now, you see nothing, because it looks just like heaven
and stars in heaven.
And actually, we also have to say that we had not enough events
and not enough beam time to get the full structure out
of these delayed pictures.
So what you then do is you just add all of those
and make a radial distribution.
So this is kind of a scattering angle of the protons.
And this is called the virtual powder and pattern, which we generated.
And these are those here.
And now you see, if you look in detail on the ground state,
5 microseconds, 10 microseconds, and look on the differences of those,
then you see that at least in the 10 microseconds case,
clearly at the high and the largest scattering angles.
So these are inverse dimensions.
So these large scattering angles are here.
These are the smaller structures.
At least the smaller structures are starting to be solved.
So there's a 50% difference between these two
at these larger scattering angles.
So this was the first kind of proof of principle experiment
that you get structural information from a large biomolecule
when it executes its function.
So with that, I think I'm over with time.
And I leave all the rest.
I'm clicking it away because I want
to come to the people who were involved, finally.
This is very important, but it takes a little while, sorry.
I had not too much time to prepare the talk because I have this new job.
So I thought I'd just stop at some point where it's reasonable.
And I didn't know how many questions you would have and so on.
It takes a little while, sorry, for that.
Do you talk to me?
Yeah, he talks.
OK.
I thought, you see, I could be much faster.
OK.
And now it comes.
So I would like to thank the Advanced Study Group.
This was a group I was running here, and they
were responsible for all the experiments at LCLS.
Important is Sasha Epp, Faten Gassnicki, Lutz Foucke, Adam Rutenko,
and Daniel Rolleis, and all the others as well, the students as well.
And Ilma Schlichting.
She's a biologist, actually, and she was instrumental also
to get all these biological samples.
I would also like to thank my former group in Heidelberg,
especially Robert Mozzama, Alexander Don, Glauzida Schroeder,
and Jose Crespo.
And I would like to thank all the people from the accelerators.
Very, very important, because as I showed you at the beginning,
we don't even know the pulses.
And we need a very, very close collaboration
with the accelerator physicists to really characterize everything
and to tune it.
We measure the pulses.
There are 100 femtoseconds.
We want to draw 40 femtoseconds.
So you go to the operator and try to convince him
to make it shorter.
Somehow he doesn't know how, but so we try that.
And so you need a very, very close collaboration.
And this worked beautiful here at FLESH,
but also in the Japanese machine and also at LCLS.
So a big thanks also to these teams.
And thank you for your attention.
Thank you.