LASER PHOTOACOUSTIC SPECTROSCOPY OF $Br_{2}$ VAPOUR IN THE YELLOW-GREEN REGION:
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Date
1994
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Ohio State University
Abstract
Discrete vibronic bands of $B \ {^{3} \pi} (ou{^{+}}) \longleftarrow X \ {^{1} \Sigma}^{+}_{g}$ transition in the $Br_{2}$ vapour imbedded on an underlying continuum primarily due to $lo {^{1} \Pi}_{lc} \ \longleftarrow X \ {^{1} \Sigma}^{+}_{g}$ transition have been recorded photoacoustically in the frequency region $17740-19680 cm^{-1}$. The relative photoacoustic intensities of the bands have been used in estimating the non-radiative de-excitation cates from the upper vibronic levels. It is found that the non-radiative relaxation rate increases with the increasing vibrational quantum number of the $B \ {^{3} \Pi} (ou{^{+}})$ state. The relative intensities of the underlying continuum has been interpreted in terms of dissociation from the ${^{1} \Pi}{_{lu}}$ repulsive state and also from the dissociation of the $B \ {^{3} \Pi} (ou{^{+}})$ state. The analysis leads to relative contributions of different mechanisms of non-radiative relaxation in the region of dissociation limit of the $B \ {^{3} \Pi} (ou{^{+}}) \longleftarrow X \ {^{1} \Sigma}^{+}_{g}$ transition viz., dissociation from the excited vibrational level of ${^{3} \Pi} (ou{^{+}})$ state, energy transfer from the ${^{3} \Pi} (ou{^{+}})$ to the ${^{1} \Pi}{_{lu}}$ state, direct excitation to the ${^{1} \Pi}{_{lu}}$ state and non-radiative relaxation from the vibronic level of $B \ {^{3} \Pi} (ou{^{+}})$ state.
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Author Institution: LASER AND SPECTROSCOPY LABORATORY, DEPARTMENT OF PHYSICS, BANARAS HINDU UNIVERSITY