THE $v_{2}$ AND $v_{5}$ INFRARED BANDS OF $H_{3}Si^{79}Br$

Abstract

The $v_{2} (A_{1})$ and $v_{5}$ (E) fundamental bands of isotopically pure $H_{3} Si^{79}$ Br, centered at 929.752 and $946.427 cm^{-1}$ respectively have been analyzed from a high resolution Fourier transform spectrum in order to improve a former $work^{1}$. These two bands strongly interact through a X-Y Coriolis resonance. We also included in the model the weak Coriolis resonance between $v_{5}$ and $2v_{3}$, with a crossing near $k\ell = -13$ and K = 14, the r-type $\ell(2. - 1)$ resonance between $k\ell = 2$ and $k\ell = -3$ of $v_{5}$, with a crossing at J = 58 and the accidental resonance $\ell (1. - 2)$ between the $(k\ell = 1.A^{2})$ levels of $v_{5}$ and $(K = 3, A^{2})$ of $v_{2}$. We made a global fit of 4200 wavenumbers for $v_{2}$ and $v_{5}$ and 630 upper state energies of $v_{3} = 2$, deduced from previously $determined^{2}$ transitions of $2v_{3} - v_{3}$ and of $v_{3}$. A few perturbation allowed transitions were also included in the fit, which gives a s. d. on residuals better than $0.00015 cm^{-1}$. A set of molecular parameters for all levels involved will be reported.