Laser-induced thermal detachment of hot, large molecular ions under multiphoton-absorption conditions

Abstract

We observed the delayed electron detachment induced by multiphoton absorption of hot, zinc phthalocyanine negative ions (C${}_{32}$H${}_{16}$N${}_{8}$Zn${}^{\ensuremath{-}}$) stored in an electrostatic ion storage ring. To examine the critical parameters and conditions that characterize the delayed processes, we performed a theoretical model simulation employing inferred values for molecular properties and experimentally controlled values of excitation laser energy and fluence. The thermal detachment rate was estimated by applying the detailed balance theory, and the internal energy distribution of the ions after multiphoton absorption was calculated as a function of the ion temperature immediately before laser irradiation. Our model simulation well reproduces the experimental results, and demonstrates that the experimental configuration determines the range of the observed detachment rate, namely the detectable energy window of the stored ions. The parameter dependence of the estimated ion temperature on the molecular properties was also obtained.