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On quantum scales, there are many second laws of thermodynamics

New research from UCL has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are generally not noticeable except on very small scales, at which point, they become increasingly important. More...

Published: Feb 10, 2015 11:55:53 AM

Spectrum of hot methane

Spectrum of hot methane in astronomical objects using a comprehensive computed line list

A powerful new model to detect life on planets outside of our solar system, more accurately than ever before, has been developed by researchers from UCL Physics & Astronomy and the University of New South Wales. More...

Published: Jun 18, 2014 4:54:56 PM

Quantum Phase Transitions

"Like melting an entire iceberg with a hot poker" – UCL scientists explore the strange world of quantum phase transitions

“What a curious feeling,” says Alice in Lewis Carroll’s tale, as she shrinks to a fraction of her size, and everything around her suddenly looks totally unfamiliar. Scientists too have to get used to these curious feelings when they examine matter on tiny scales and at low temperatures: all the behaviour we are used to seeing around us is turned on its head. More...

Published: May 13, 2014 4:06:57 PM

Professor W Roy Newell

Email w.r.newell@ucl.ac.uk
Telephone +44 (0) 20 7679 7140

Research Profile

The general theme of the current research is the interaction of laser radiation with atomic matter, collisional processes in laser fields and atomic scattering phenomena. While the work is of a fundamental nature there is ample application in environmental physics and the physics of fusion plasmas. The use of computers for data transfer, modelling and covariance mapping is a path-way to techniques used in commerce.

Intense Laser Fields

In the interaction of short pulse (10-9 s - 10-14 s) high intensity radiation with molecules we study the fragmentation processes of molecules in laser fields of 1017  W/cm2 . This intensity is greater than that existing between the electron and proton in the ground state of atomic hydrogen. The dynamics of the molecule, re-orientation and symmetry changes are determined using a newly developed momentum imaging technique in which the molecular structure is imaged on a detector using the Coulomb explosion of the molecule. In a 30 fs pulse all natural molecular rotation and vibration is frozen during the interaction. New processes of molecular interactions with intense light fields are revealed.

Collision Processes in Laser Fields

In this area of research we study the interaction of free electrons with atoms and molecules while dressed by a laser field. The electron and atom can virtually exchange photons with the laser field before and after a collision. Only when a real collision occurs does the virtually dressed electron retain the extra photon energy and the structureless electron speeds up. This is Free-Free scattering. Additionally the combined energy, E, of an electron and n virtually absorbed photons, E + nhv, can cause excitation of real states of energy Ex when E < Ex . This process is Simultaneous Electron Photon Excitation (SEPE) and is the electron-photon analogue of two photon excitation.

Scattering Phenomena

Using High Resolution Electron Energy Loss Spectroscopy (HREELS) we measure the cross sections for excitation processes in molecules of atmospheric interest. In particular we study scattering from molecular excited states.

Facilities

Good laser facilities providing 6 ns pulses with 0.8J/pulse at 1064 nm and 532 nm and 30 to 200 ps pulses with 60 microJ/pulse are available; also a continuous 400 W CO2 laser system is operational. In addition to the laser systems, several atomic scattering apparatus, HREELS and TOF, are available. Modern computer controlled data acquisition systems are in use.

Femtosecond laser pulses are available at the ASTRA facility at RAL.

The group currently has one PDRA and three research students. There are established collaborations with RAL, QUB and TMU.

Page last modified on 06 mar 08 18:49