Time resolved spectroscopy of xenon excimers excited by synchrotron radiation

Implementation of the interacting quantum atom energy decomposition using the CASPT2 method

We present an implementation of the interacting quantum atom (IQA) energy decomposition scheme using the complete active space second-order perturbation theory (CASPT2). This combination yields a real-space interpretation tool with a proper account of the static and dynamic correlation that is particularly relevant for the description of processes in electronic excited states. The IQA/CASPT2 approach allows determination of the energy redistribution that takes place along a photophysical/photochemical deactivation path in terms of self- and interatomic contributions. The applicability of the method is illustrated by the description of representative processes spanning different bonding regimes: noble gas excimer and exciplex formation, the reaction of ozone with a chlorine atom, and the photodissociations of formaldehyde and cyclobutane. These examples show the versatility of using CASPT2 with the significant information provided by the IQA partition to describe chemical processes with a large multiconfigurational character.

Efficient population inversion in excimer states by supersonic expansion of discharge plasmas

Laser emission at 126 nm has been obtained from excimers of Ar(2) excited electrically in a nozzle discharge followed by supersonic expansion. The direct measurement of light amplification with a tunable VUV probe leads to a gain of >3 cm(-1). This high gain arises from efficient population inversion of low vibrational and rotational levels of the excimer state brought about by the supersonic expansion and cooling of the discharge plasma.