THE 3d BROMIDE SERIES: THE PURE ROTATIONAL SPECTRUM OF CrBr (X6Σ+)

Abstract

The millimeter-wave spectrum of the high spin radical chromium bromide, CrBr, in its X$^{6}\Sigma^{+}$ state has been measured using direct absorption methods between 220-300 GHz. The radical was created in a DC discharge by the reaction of dibromomethane with chromium vapor, produced in a Broida-type oven. This study is the first measurement of CrBr by any spectroscopic technique. Eight rotational transitions of four isotopologues ($^{52}$Cr$^{79}$Br, $^{52}$Cr$^{81}$Br, $^{53}$Cr$^{79}$Br, and $^{53}$Cr$^{81}$Br) of this radical were recorded in the ground vibrational state, each consisting of fine structure sextets with additional bromine hyperfine splitting. Spectra were also obtained for the v=1 and v=2 states of $^{52}$Cr$^{81}$Br and $^{52}$Cr$^{79}$Br. The data were fit with a Hund’s case b Hamiltonian and rotational, spin-spin, spin-rotation and hyperfine parameters were determined, including the higher order spin terms $\gamma_{s}$ and $\it{\Theta}$. The hyperfine constants indicate that CrBr has a significant covalent component to its bonding, unlike its chlorine and fluorine counterparts.