Abstract

Methyl iodide is a popular molecule for spectroscopic and dynamic studies.^1–6 The lowest excited electronic state (à state) is repulsive along the C—I bond and dissociates in about 100 fs,¹ The next higher series of states (B̃ and C̃) are due to (5P → 6s) excitations and are Rydberg in character.² These states undergo rapid predissociation to the à state; however, there is considerable disagreement regarding the decay rates and whether there is vibrational specificity.^3–5 We record the spectroscopy of the B̃ and C̃ Rydberg states of CH₃I and CD₃I rovibrationally cooled in a supersonic molecular beam. Two types of spectra are recorded: one-photon direct absorption spectra and one-photon resonance, one-photon ionization spectra. The present spectra are higher in resolution than in previous studies and allow the vibronic-specific rates of predissociation to be determined.

© 1992 Optical Society of America