Dr I.C. Lane
BSc (Nottingham), 1989
PhD (Nottingham), 1993
Lecturer in Physical Chemistry
Tel: + 44 (0) 28 9097 5470 / 4458
Fax: + 44 (0) 28 9097 6524
The research in my group concentrates on studying the fundamental physical processes behind chemical reactions using novel tehniques and the latest technology. The ultimate goal is to study reactions that have never been seen observed before in our Universe! Read on and all will be revealed…
It is comforting to know that in a stressed-out world where speed is worshiped that there really are some things better achieved by sloth. At room temperature, molecules and atoms possess truly awesome speeds: you may think that a Formula One car is fast but its peanuts compared to a hydrogen molecule.
These huge velocities are sometimes a real pain. If you want to control or measure the property of something very accurately, you don’t want it moving around too quickly (try measuring the height of a 100m runner while she's sprinting to the gym). A powerful technique for investigating matter is spectroscopy, which measures the tiny differences in internal energy that a microscopic object can possess (these so-called energy levels are due to quantum mechanics, a course I teach at Queen’s). The accuracy of this measurement is affected by the speed of the object: if the speed is high, we cannot get such a good fix on the true energy separation as we can when the object is sluggish. Slow objects have other interesting properties too: as the speed falls, they act less like particles and more like waves. This leads to all kinds of strange and wonderful behaviour, like forming interference patterns, apparently being in two places at once and cats that are both dead and alive simultaneously.
Slowing down a car is easy: apply the brakes. However, you could also slow it down by throwing heavy objects at it, such as a wall (not recommended for drivers). We can reduce the speed of atoms by using a similar principle but using photons of light instead of heavy objects. This clever technique is called laser cooling. Cooling is of course nothing new: but cooling without an avoidable change in phase (gas – liquid – solid) is. Every chemist knows that if you cool a vapour of atoms, it first becomes a liquid and then a solid. Well, not necessarily. If we cool gaseous atoms with a laser, the individual atoms slow down to a near halt but they remain in the gas phase (because of the low density). Yes, it is a bit weird that shining powerful laser light can cool atoms instead of heating them but it can if you do it right. Physicists have had fun with this for ages, but now chemists are getting in on the act. For chemists, atoms in the p-block are of particular interest because all the really interesting chemistry involves these sorts of atoms but until now none have been laser cooled.
We have so far designed an experiment to study the cooling of gallium atoms. Gallium is ideal because it acts as a good model for all the p-block elements: its cooling wavelength is also accessible by commercial diode (i.e. cheap) lasers and slow, laser cooled atoms could be used to make tiny semiconductor devices that will take man to Mars (okay, I am getting ahead of myself here). However, it is not an easy atom to cool and we are developing new and novel laser cooling methods to slow them down. We are using revolutionary blue diode lasers that you will see soon in the next generation of DVD players to do this. By using two lasers, it should be possible to create the cycles of absorption and emission that are necessary to remove the kinetic energy of the atoms (see the energy level diagram below).
This will be followed by the development of a velocity selective atomic beam, using laser cooling to control the mean speed of beam of atoms. Preliminary work here will focus on the alkali metals and on gallium.
Once slowed, we hope to use them to study low temperature collisions which are dominated by the wave-like nature of the atoms. Theoretically, we can model the collisions of atoms if we know the potential energy between the atoms as a function of their separation. These calculations are carried out using sophisticated computer codes. We have calculated new potential energy curves for the Ga2 molecule, and are calculating important surfaces for the Ga3 molecule. The latter will be useful in understanding the physics behind the formation of Ga2 molecules by three-body collisions at ultracold temperatures, which leads us neatly to.....
The Big-bang theory suggests that the Universe began as a fiery ball that expanded and cooled to the present temperature of deep space- about 2 Kelvin (this is colder than liquid helium-4, though not as cold as liquid helium-3). Therefore, reactions at colder temperatures have never taken place before in the Universe. In labs today, however, we can routinely cool atoms down to temperature of just 1 micro Kelvin (one millionth of a degree) or less! Today, even diatomic molecules at 20 nano Kelvin (1 nano Kelvin = one billionth of a degree) have been seen in a gas locked in an optical trap.
These trapped molecules may undergo collisions with other cold atoms- to produce new molecules distinct from the original. This is ultracold chemistry. Since the molecule and atoms are at temperatures below 2K, the resulting chemistry is taking place at temperatures never before achieved in our universe. An example is
This exothermic reaction involves the Ca2 molecule which has a very, very weak bond and is unlikely to have been created before in the interstellar environment.
We can even study chemical reactions that have never been possible before the invention of laser cooling because they can only take place at temperatures below 2K! We are currently investigating such reactions theoretically…. And hopefully will one day experimentally!!
If any of my research has fired your imagination, you can always email questions or comments to me at firstname.lastname@example.org. If you are interested in working on these projects, please drop me a line as well.
In addition to my main research, I am collaborating with a number of colleagues on other projects such as chiral surfaces (with Dr Malcolm Kadodwala at Glasgow) and chiral switching of transition metal complexes (with Dr Nick Fletcher here at Queen’s).