The influence of orbital-rotation coupling on electronic transitions of isolated molecules: Angular momentum dependence of radiative transition in S1 pyridine

High resolution optothermal spectroscopy of pyridine in the S1 state

“…The rotational constants, AЈ, BЈ and especially CЈ, given in Table I for the 0 0 S 1 level differ significantly from those of a past report. 9 Im-proved frequency resolution and a better suppression of hot band signals with our instrumentation results in a higher accuracy in the determination of these constants.…”

“…9 Contour fits for all five vibronic bands were performed with and without the inclusion of axis-switching. In all cases, there was a small improvement in the standard deviation assuming the occurrence of axis-switching although the rotational constants were not appreciably different.…”

“…In subsequent studies with slightly higher spectral resolution ͑using the same pulsed laser, but with intracavity étalon͒ it was reported that the fluorescence quantum yield does not vary across the rotational envelope of the ͑0-0͒ S 1 ←S 0 band. 9,10 In this paper we report high resolution measurements of several S 1 ←S 0 vibronic transitions of pyridine in a continuous supersonic molecular beam, using optothermal ͑OT͒ detection. Recently we demonstrated the advantages of this technique measuring OT spectra of weakly fluorescent systems, such as s-tetrazine and dimethyl-s-tetrazine, with a signal to noise ratio much larger than obtained by LIF detection under similar excitation conditions.…”