Transient vibrational spectroscopy by flash photolysis stimulated emission pumping: 3ngr;2of singlet methylene

摘要

A vibrationndash;rotation spectroscopic method based on stimulated emission pumping has been developed for transient molecules generated by flash photolysis. This method may be generally applicable to radicals with electronic excited states accessible by visible or UV laser pulses. This first demonstration on the bendingv2=3 level ofatilde;thinsp;1A1CH2generated a vibrational term value of 3950.45(7) cmminus;1and the rotational constantsA=25.665(40),B=11.470(7), andC=6.7140(61) cmminus;1. These constants indicate that the 3ngr;2level is well below the bendinghyphen;potential barrier. Perturbations of several rotational levels by the triplet state are identified. In addition, and most interestingly, abnormally intense Dgr;Ka=3 transitions were observed in theatilde;larr;btilde; 2163band.