Resonance Raman scattering from isotopically pure and natural bromine vapor

Abstract

We have recorded high‐resolution resonance Raman spectra of the bromine molecule in its natural abundance and as pure isotopic molecules ⁷⁹Br₂ and ⁸¹Br₂ with excitation by light which is in resonance with the continuum of the B(³Π)‐state. The observed spectra are characterized by a progression of vibrational lines up to the tenth harmonic. These lines display complex structure which can be explained in terms of Q branches, S band heads, unresolved O branches and vibrational ‘hot’ bands. The assignment of all observed lines is based on Fortrat diagrams which have been calculated by using spectroscopic constants derived from high resolution absorption spectra and on depolarization measurements. The vibrational constants ω_e, ω_ex_e and ω_ey_e and the rotational constants B_e and α_e for the X (¹Σ)‐state of bromine were determined independently from the Raman spectra. Variations of the spectral band shape of the fundamental and the overtones were observed using five different exciting lines of the argon ion laser. The band shapes were also studied while changing the laser power which affects the spectroscopic temperature. A qualitative discussion of the observed changes is given.