Eur. Phys. J. D 55, 627-635 (2009)
https://doi.org/10.1140/epjd/e2009-00283-5

Time-dependent delayed electron spectra: a direct measurement of total decay rate as a function of internal energy

Laboratoire de Spectrométrie Ionique et Moléculaire, UMR CNRS 5579, Université Lyon 1, 69622 Villeurbanne, France

Corresponding author: ^a bordas@lasim.univ-lyon1.fr

Received: 30 April 2009
Revised: 3 August 2009
Published online: 6 November 2009

Abstract

We present a general method to measure internal energy dependant decay rate in the case of systems emitting thermal electrons. Our approach is based on the measurement of the time-dependent kinetic energy spectra of delayed electrons using time-resolved velocity map imaging spectrometry. We illustrate this method in the case of C₆₀ molecules. Indeed electron spectra for C₆₀ have been studied in great details in the past few years, allowing a complete analysis of the observed features. Moreover, C₆₀ offers the opportunity to study competing decay mechanisms demonstrating that the technique may have broader applicability to other molecules. Using a model that includes all contributing decay channels relevant in our time delay range (namely delayed ionization and dissociation by C₂ emission) we are able to derive quantitative information on the decay channels of the molecule. In the situation considered here, the time-dependent electron temperature extracted from the kinetic energy spectra is used to determine more precisely the rate constant for the dominant process, namely neutral C₂ dissociation channel. In other words, the measurement of the cooling of an ensemble of C₆₀ molecules as a function of time delay after heating provides a direct and quantitative access to its decay dynamics. This method may be used to map out the total rate for complex decay mechanisms.