Dr Peter Hammond Publications List
The thrust of my experimental research has been to invent and develop experimental approaches that allow the study of atomic and molecular states that are very difficult, or impossible, to observe using existing experimental methodologies. The interest in the particular excited states targeted in these new experiments are that electron-electron correlations play an important role in the state formation and stability.
The most recent technique developed enables the observation of energetically narrow, and hence long lived, highly excited states formed by photon impact using extreme ultra violet light derived from a synchrotron radiation source. In the most recent experiments two previously unobserved series of doubly excited states in helium have been detected, despite helium having attracted the most intense experimental scrutiny over the last thirty years.
In a related experiment, but using electron impact, the decay products of highly excited states are separated using a momentum recoil technique to isolate the decay product, which in conventional experiments is embedded in a large signal from other excitation processes.
The momentum recoil spectrometer was developed for a related experiment in which atoms or molecules were excited to metastable singly excited states followed by a second excitation step using a narrow linewidth, pulsed photon beam formed by a frequency double pulsed dye laser. This experiment allows the study of the rotational structure of molecules formed by electron impact, a detail which has been previously inaccessible.
All three experiments provide new ways forward for experimental atomic and molecular physics where quantum dynamical descriptions of atoms and molecules can be explored in detail and clarity.
Some of the early history of this work in Helium can be found on this site (He)
"High-lying long-lived doubly excited
states near ionization thresholds of helium",
E Sokell, AA Wills, P Hammond, MA MacDonald and M K Odling-Smee,
Journal
of Physics B (1996) 29, L863-71
"Radiative Decay of Doubly Excited States in Helium below the He+ (N
= 2) Ionization Threshold",
M. K. Odling-Smee, E. Sokell, P. Hammond, and M. A. MacDonald,
Physical Review Letters
(2000) 84, 2598-2601
"Observation of Triplet Doubly Excited States in Single Photon Excitation
from Ground State Helium"
F. Penent, P. Lablanquie, R. I. Hall, M. Zitnik, K. Buar, S. Stranges, R.
Richter, M. Alagia, P. Hammond, and J. G. Lambourne
Physical Review Letters
(2001) 86, 2758-2761
"A novel spectrometer
combining laser and electron excitation and deflection of atoms and
molecules"
Andrew J. Murray & Peter Hammond
Review
of Scientific Instruments (1999) 70, 1939-1950
"Laser Probing of Metastable Atoms and
Molecules Deflected by Electron Impact"
A. J. Murray and P. Hammond
Physical Review Letters
(1999 ) 82, 4799-4802