High-Resolution Photofragment Spectroscopy Of The Gas-Phase Methyl-Iodide Ion

Photodissociation spectra of the molecular ion CH3I+ were obtained with a three stage quadrupole mass spectrometer. Starting from the ground state, theÃ2E1/2 state was excited with a stilbene 3 cw dye laser. This state predissociates to CH+3+I. Measuring the intensity of the CH+3 fragment ions as a function of the wavelength of the exciting laser, a spectrum showing vibrational and rotational structure was obtained. The vibrational structure was assigned to three progressions ofv3 and new vibrational frequencies were determined. From a computer simulation of the (0, 1, 10) band rotational constants were derived. In particular, their dependence on the vibrationv3 was studied.