Clover leaf by Scott Robinson on Flickr

Quantum mechanics explains efficiency of photosynthesis

Light-gathering macromolecules in plant cells transfer energy by taking advantage of molecular vibrations whose physical descriptions have no equivalents in classical physics, according to the first unambiguous theoretical evidence of quantum effects in photosynthesis published today in the journal Nature Communications. More...

Published: Jan 9, 2014 3:48:33 PM

Free Electron Lasers and Attosecond Light Sources Conference

UCL is hosting a conference on Free Electron Laser and Attosecond-Strong Field Science from June 30 to July 2 2014 at UCL. The preliminary  web-page for the conference is now live at
http://www.ucl.ac.uk/phys/amopp/atto-fel-conference More...

Published: Oct 1, 2013 2:24:13 PM

Macroscopic and microscopic work.

Quantum engines must break down

Our present understanding of thermodynamics is fundamentally incorrect if applied to small systems and needs to be modified, according to new research from University College London (UCL) and the University of Gdańsk. The work establishes new laws in the rapidly emerging field of quantum thermodynamics. More...

Published: Jun 27, 2013 9:40:58 AM

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.


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.

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