HIGH RESOLUTION THRESHOLD PHOTOELECTRON COINCIDENCE SPECTROSCOPY
AT ELETTRA

F. Penent1, P. Lablanquie2 , R.I. Hall1, J.H.D. Eland2, L. Avaldi4, R.
Camilloni4, S. Stranges5, M. Coreno6 and K.C. Prince7


1 DIAM, Universit=E9 P & M Curie, 75252 Paris Cx 05, France
2 LURE, Universit=E9 Paris-Sud, BP34, 91898 Orsay, France
3 Physical and Theoretical Chemistry Laboratory, Oxford University,
Oxford
         OX1 3QZ, UK
4 IMAI del CNR, 00016 Montelibretti, Rome, Italy
5 Dipartimento di Chimica, Universita degli Studi di Roma, 00185 Rome,
Italy
6INFM, TASC Laboratory, Trieste, Italy 7Sincrotrone Trieste, 34012
Trieste, Italy


Double photo-ionisation of rare gases (Ar, Ne) and molecules (N2, CO,
CO2) has been studied by means of Threshold PhotoElectrons Coincidence
spectroscopy on the Gas Phase beam line at Elettra. With the available
photon energy resolution of 20,000 it is a challenge to reach a similar
resolution for detection of electron pairs formed at threshold. A
resolution down to 5 meV was observed for Ar++ while for other dications
only a 10-15 meV resolution was observed. Nevertheless, vibrational
levels of the 3Sg- state of CO2++ are clearly resolved.