Molecules in Intense Laser Fields

Abstract

Recent advances in tunable laser sources have stimulated a great deal of interest in the study of intense field-matter interaction physics. Whenever a molecule interacts with an intense radiation field, it can absorb multiple photons from the field and make a transition either to an excited state (excitation) or into the continuum (ionization). If the energy of an integral number of photons equals the energy difference between the initial and an excited state, the multiphoton process becomes resonant and its probability is greatly enhanced. The observation of such resonant enhanced processes requires considerably less intensity than that required for non-resonant processes. Several researchers have taken advantage of this resonance enhancement to study various aspects of resonant enhanced multiphoton ionization (REMPI) processes in molecules.¹ Measurement of ionic and photoelectron spectra have illustrated features such as non-Franck-Condon effects in ionic vibrational branching ratios due to autoionization,² shape resonances³ and Cooper minima,⁴ non-atomic effects in ionization of Rydberg states⁵ and competition between rotational and vibrational autoionization.⁶

Keywords

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