Unconventional techniques in laser spectroscopy

A3Pi1u<--X1Sigmag+ laser photoacoustic spectroscopy of Br2 vapor in the extreme red wavelength region 665-720 nm

The A3Pi1u<--X1Sigmag+ photoacoustic spectrum of Br2 vapor has been studied and vibronic analysis performed using earlier data available for this system of bands from optical spectroscopy in the region 665-720 nm. The vibronic levels involved in these transitions are 4< or =v'< or =21 and 1< or =v''< or =4. The relative photoacoustic intensities of the vibronic bands have been used in estimating the non-radiative relaxation rate from vibrational levels of A3Pi(1u) state. The non-radiative relaxation is found to be a nonlinear function of the upper state vibrational quantum number. The radiative rate constants for the A3Pi(1u) state vibrational levels have been compared with the corresponding non-radiative constants obtained from present work. Non-radiative decay rate constants for the vibrational levels of A3Pi(1u) state have been experimentally determined for the first time from photoacoustic spectrum of Br2 vapor in the extreme red region.

Photoacoustic spectrum of iodine in the 490-680-nm (20402-14700-cm(-1)) region

Vibronically resolved laser photoacoustic spectra of I(2) vapor have been recorded at room temperature in the presence and absence of atmospheric air in the 490-680 nm (20402-14700 cm(-1)) region for what is, to our knowledge, the first time. The vibrational bands belong to the B(3)Pi(O(u)(+)) ? X(1)Sigma(g)(+) transition, but the underlying continuum also results from the (1)Pi(1u) ? X (1)Sigma(g)(+) and A (3)Pi(1u) ? X (1)aSigma(g)(+) transitions. The mechanisms of photoacoustic signal generation are discussed by analyzing the photoacoustic intensity in light of Franck-Condon factors for the B ? X transition. Energy transfer to O(2) caused by the photodissociation of I(2) into (2)P(?) + (2)P((1/2)) I atoms is obrved in the presence of atmospheric air, and the predissociation of the B state has been observed for its vibrational levels v' ~ 23-27.