Effect of electronic states coupling on methyl torsion in 3-methylisoquinoline

Spectroscopic studies on jet cooled 3-methylisoquinoline using fluorescence excitation and dispersed fluorescence methods were carried out. The effect of methyl substitution on the excited state behavior of isoquinoline is focused. Methyl torsional behavior and the effect on torsional potential of methyl group due to excited states mixing are addressed. The possible explanations of the observed intensity pattern of the torsional transitions in the fluorescence excitation spectrum are also presented.