Knowledge Bank

Two--photon resonant multiphoton ionization has been used to prepare rotationally cooled and selected $CH3I+$ ions with controlled vibrational and electronic distributions. These ions are photodissociated by a second laser. The highly simplified photodissociation spectrum displays a clear dissociation threshold as well as bands hidden in earlier spectra. The data suggest corrections to previously determined vibrational constants. The electronic transition studied corresponds to excitation of a nonbonding $5p\pi$ electron to a 6s molecular Rydberg orbital on an ion core of the ground configuration. The bare ion core in this configuration has $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\pi 1/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\pi 3/2$ sates which are separated by about $5000cm-1$ by strong spin orbit coupling. Time-of-flight photoelectron spectroscopy has been used to study the branching ratio of the channels to $\pi 1/2$ and $\pi 3/2$ ionization.