We are at the [diamond] [light] source just outside Oxford in England
[we're] here for the next week or so [to] do an experiment and we are standing in the synchrotron right now
You can see it all around [I]
Think that [one] is a particle accelerator
Where electrons are circulated around put in a roughly circular or a pretty well circular trajectory?
Very very very close to the speed of light. We are not so much interested on like Particle physicists
We're not so much interested in the particles of themselves what we are interested in for our
experiments is the fact that when you take a charged particle like an electron and
Circulate it very very close to the speed [of] light or accelerate it very close to speed of light
What it does is it gives off?
What's called synchrotron radiation. So this is radiation that goes all the way from infrared up to very very hard very very [high-energy]
X-Rays and we as condensed Matter physicists solid-state physicist nano scientists
Whatever you want to call us what we are most interested in is harnessing that light
Shining it onto a sample and learning about what the atoms and molecules
And that sample are doing we walk around is there's a sort of hissing noise
And the hissing noise comes from nitrogen gas now because of this very bright light that we have it's very very focused
But it can get quite hot so we are standing right above. What is called Beamline eyes zero name
What's a beam line? Well? You have the electrons circulating around. How do you get the light out well?
What happens is you have tubes funnels
through which the light travels and also as you can see
Us going off into the distance you might be able to see this in terms of just coming off
tangentially to the to the ring
We're on the surfaces and interfaces line just here just down here and we will be collecting that light
Coming from those electrons and shining it onto our sample down in this experimental hatch down here
So to get beam time you have to like anything in science
you have to write a grant proposal you have to get the time you have to get the funding for the work and
We wrote that proposal quite some time ago almost a year ago now
So we were hugely excited when we got the time and they were hugely excited to be here to actually be able to exploit this
Synchrotron radiation
So what we're looking at here is obviously we need to have optics to get this light down
But this isn't optics these are X-Ray optics
And we need to be able to get those x-rays onto our sample to focus them down the synchrotron is about 10
billion times Brighter than the sun
So this is an immense engineering challenge with very very clever people doing this work
To ensure that we can get that those very bright x-Rays and get them on to our sample
so that [the] Tube you can see
Coming down here is actually the tube that is carrying the beam [to] [our] to our chamber, and it's also a high vacuum
So it's a pressure comparable to that you get on the surface of the moon the electrons are not [allowed] to the electrons are basically
Circulating away over there what [we're] what is coming down
This Tube is the light generated by those electrons, and that's going to come into or similarly ultra high vacuum chamber
We're going to have those x-rays and they're going to impinge on our sample
And then we're going to find out wonderful things about our particular molecule
We're in the experimental hochberg
This is where we actually do the experiments and the light actually comes in through this Tube here
And then we're going to chase out through the tumors ETc some more optics some
very tips of
Diagnosis, and then we're coming all along all along
Into our experimental chamber here. It's an ultra high vacuum Chamber [Stainless-steel]
Pressure in here very very low again comparable to the surface of the moon and our sample sits in there
So the beam is coming into our chamber, and it's going to the beam is going to hit our sample
And it's going to eject the electrons out and we want to measure the energies at which those electrons come out
It's actually something called the photoelectric effect which it wasn't for a relativity that Einstein won. His nobel prize
It was actually for the photoelectric effect something called photon emission
that's what we're doing here one part just one part of what we're doing here photons in, electrons out and
Every material has [its] own signature in terms of its photo emission spectrum, so this is our electron energy analyzer this wonderful
hemispherical analyzer
and it's literally called a hemispherical analyzer and
The way we measured the energies [of] the electrons is that we have a couple of spheres in here, and we put a voltage on
those spheres and then what we do is we [clear] off the
centripetal
Force on the electrons against that that voltage so we play off the centripetal force against the electrostatic force and
only those electrons that I've got the right and
Kinetic energy the right speed are actually going to make it through and then we vary the voltages and we can collect a spectrum that
way
Precisely, that's exactly what it does. It's an energy pencil. So it it allows us to detect how many electrons
We've got of a certain energy all these different arms
you can see
It's also allowing us to move samples around in vacuum without
Breaking the vacuum and so we can use these arms to move the sample around
What they're doing over here? What Sam's doing at the moment is sorting out?
The the important aspects that this experiment [let] me tell you about the experiment
We're going to do so this is the [molecule] were interested, and it's a absolutely fascinating molecule
It's a [C60] it's [a] what's called a Buckminsterfullerene
We've got a single water molecule, and this is made. We don't make this we're not half clever enough
We are physicist we are not clever enough to do this. This is made by our colleagues in Southampton
They do something called molecular surgery they open up a hole in the cage
they drop a water molecule in and then they seal up the hole just with wet chemistry it's
Phenomenal the water molecule is trapped within the kids. It's in kids its incarcerated within within this molecule
Why is that interesting [well] first of all you've got a single water molecule not interacting with any other water molecules
[this] is not something you find very often in nature the C60 is about a nanometer across once you confine
Molecules once you confine atoms and once you confine particles to small spaces
That's when you start to see very interesting quantum effects
What we're really interested [in] is can we exploit those effects when we take this molecule and put it down onto a surface
And the first question to ask is when you put it down onto a surface and the cage bonds to the surface does the molecule
Inside does the water molecule feel the effect of the surface
Or is this just like a faraday cage does it completely screen it out
So that [the] water molecule doesn't see the surface there are a number of different things
We do both up the first is to exploit this photoelectric effect this photo emission effect photons come in
We excite electrons out [of] the oxygen and we can look at the spectrum [of] those
Electrons to work out, what's happening with the water molecule? Where do we get those photons?
Well we get them from the [beamline] why do we need the beamline and why is a synchrotron?
Why don't we just do this with an X-Ray source back in Nottingham?
Why don't we do [it] in a lab the great thing about a synchrotron?
Is that you can tune the photon energy?
across a very wide range in this case from hundred Electron volts of the killer Electron volts that's a
Remarkable tool because we can tune in on [particular] parts of the spectrum and work out what's going on the challenge of this experiment?
it's a really fun experiment to do is we take a silver surface which everybody is busily preparing at the moment and
We're going to put our molecules down onto that surface the first challenge is how do we get the molecules down into the surface?
well what we do fortunately would [C60] we can take it as a powder, and that's how we
guess we get about a milligram of these molecules at the black powder we put it into an oven it's literally an oven and
We [bolt] [it] [onto] the chamber
We heat it up and the molecules very nicely
Sublime they go directly from the solid phase to the gas phase and they stream off as a beam of molecules
They hit the surface and they stick and if we do that in just the right way
It's [taking] us a bit of time to work out just
What that [right] way is what if we do it in just the right [way]?
Then you can get a nice ordered film an ordered mono layer a single layer of molecules on the surface
Then we take a beam of photons
They come in and we look at the electrons of a given out by the water we also interested actually in the kids itself
So we also look at the electrons coming out from the carbon
That's the first stage of the experiment, but [actually] the technique. [we'll] use in here
in parallel
And a real advantage of this particular beam line because it can do this technique. It's something called X-Ray standing with analysis and that's
That is a fascinating technique and here's where my lack of a crystal comes into play what we do is. We have a crystal
There's [a] surface of a crystal. We have planes of atoms
What we have here is our beam coming in now if we tune our photon energy of [our] beam
To something called the Bragg Condition right what that means is if we get the wavelength of our beam?
So it's the right is the same size as the spacing of the crystals well half of the crystal planes
What will happen is that the beam will get diffracted?
So we have a beam coming in here, and we have a beam diffracted which comes back out
and when those two beams interfere
What happens is we get to get something which is called a standing wave it's pretty well exactly what happens on a guitar string you
get a standing wave [set] [up] [on] a guitar string in terms of the interference of [travelling] waves on a guitar string and
Now the great [thing] is if we have our molecule at the surface
We have this standing wave field which has got a periodicity
It's a weird so it's got a periodicity the molecule bears in this
Wave that's the best way of thinking about it. You've got the molecule
Which is sitting in this wave field and if you change the energy of the incoming beam
just a little bit what you can do is you can tune the Maxima and minima you can shift them back and forth [and]
By shifting them back and forth you shift them back and Forth through the oxygen
And then what happens is if you look at the electrons coming out from the oxygen you will see a characteristic profile
depending on where the
Water molecule is sitting with respect to the surface planes the reason we're doing all [of] this is to find out where in the kids
The molecule is sitting and moreover
We're not even restricted to those planes what we can do is you can rotate our sample and we can triangulate?
the position after we do the same thing again and
Triangulate the position of a single molecule within the cage we have done some preliminary work [were] fairly confident
It's going to be sitting fairly close to the key to the center of the cage which is
Relatively surprising because when these molecules when the fullerene molecules go down onto the surface, what happens is was charged
from the silver surface
Electrons go into the molecule bonds are quite strong bond and yet the water just sits in the middle of the kids [well]
I don't care what seemed seemingly does it seems to be completely screened from its environment
Which in terms of actually being able to exploit this effect to be able to look at those?
That water molecule explode in a device for example is really [quite] interesting
Good luck Tim [laughing] they are going to turn on the beam we will be fried we will absolutely be fried
You're looking into the chamber absolutely
so you're looking into the preparation one of the preparation chambers this thing coming down with the bellows is a
Manipulator that allows us to move the sample up and down. You've got all these various
What are called feedthroughs?
Which allow you to feed electrical signals in and out from [the] sample for example to heat it for example or to measure the temperature?
Of the sample the windows are obviously obviously this is a wonderful invention called a leak valve
It allows you to leak in very very small [quantities] of gas
And that's what we need to do to prepare our sample. What we do is
We bombarded with argon ions business is happening here in [terms] of the measurement is happening and over here in these chambers over here
That's where the beam yeah in terms of where the beam hits the sample and here is going to our analyzer
This large cylindrical Tube. This is [our] analyzer
Thank you
for 10 weeks
[I] think I guess yeah by 10 weeks since we did the beam time so we've done some analysis
And when I say we I'm using the royal way, I must admit. I have not been heavily involved with the analysis. It's been driven