The vibrational structure of bromocyanoacetylene cation in the X̃2π and Ã2π electronic states studied by emission and laser exci

Abstract

The vibrational frequencies of bromocyanoacetylene cation in its ground and first excited electronic states have been obtained by recording and analysing the emission and laser excitation spectra of the à 2 π- X̃ 2 π transition. In the emission experiments the ions are produced rotationally cooled to ca. 10 K by means of a supersonic free jet and in the laser excitation measurements to ca. 100 K by Penning ionisation followed by collisional relaxation. The resulting narrowing of the vibronic bands in the spectra is such that the vibrational frequencies of most of the fundamentals could be inferred to within ± 2 cm −1.