Emission and laser-induced excitation spectra of rotationally cooled perfluoro-2,4-hexadiyne cation (Ã2Eu↔X2Eg) and photoelectron–photon coincidence studies of the Ã2Eu state
Abstract
The Ã2Eu↔X2Eg band system of rotationally and vibrationally cooled perfluoro-2,4-hexadiyne cation has been studied by emission and excitation spectroscopies. The emission spectrum was obtained by electron-impact excitation of a seeded supersonic free jet and the excitation spectrum by laser-induced fluorescence on cations produced by Penning ionisation. From these spectra the vibrational frequencies of the totally symmetric fundamentals could be inferred for the X2Eg and Ã2Eu state to an accuracy of ±2 or ±5 cm–1, respectively. The relaxation behaviour of the excited cation has been quantitatively followed by photoelectron–photon coincidence measurements. These yield fluorescence quantum yields and lifetimes of the state-selected cation and hence the radiative and radiationless rate constants of the decay channels.