LIFETIMES OF THE \~{B} STATE OF $CH_{3} I$ AND $CD_{3} I$ USING FEMTOSECOND RESONANCE ENHANCED MULTIPHOTON IONIZATION

Abstract

Author Institution: Code 6111, Chemistry Division, Naval Research LaboratoryFemtosecond pulses in the deep uv (near 200 nm) have been used to directly measure The $\widetilde{B}$ state lifetimes for gas phase $CH_{3}I$ and $CD_{3}I$ by time-resolved MPI. Tunable deep uv femtosecond excitation pulses were generated by sum frequency generation in BBO of a frequency doubled CPM laser with amplified portions of continuum. For the vibrationless state of $CH_{3}I (CD_{3}I)$ the lifetime is 1.38 ps (1.84 psec). It is longer for the $\nu_{3}=1$ level of $CH_{3}I$ (1.80 ps). These values indicate the multidimensional nature of the dissociation and their isotopic and mode dependence will be compared with those obtained by indirect measurements