The A 6Σ+-X 6Σ+ transition of CrH, Einstein coefficients, and an improved description of the A state

The spectrum of CrH has been reinvestigated in the $\text{9000–15\hspace{0.05em}000\hspace{0.05em}}{\mathrm{cm}}^{\mathrm{-1}}$ region using the Fourier transform spectrometer of the National Solar Observatory. The 1-0 and 1-1 bands of the ${\mathrm{A }}^6{\Sigma }^{+}{\mathrm{-X }}^6{\Sigma }^{+}$ transition have been measured and improved spectroscopic constants have been determined. A value for the 2-0 band origin has been obtained from the band head using estimated spectroscopic constants. These data provide a set of much improved equilibrium vibrational and rotational constants for the ${\mathrm{A }}^6{\Sigma }^{+}$ state. An accurate description of the $\mathrm{A-X}$ transition has been obtained using a multireference configuration interaction approach. The inclusion of both scalar relativity and Cr $\text{3s3p}$ correlation are required to obtain a good description of both states. The ab initio computed Einstein coefficients and radiative lifetimes are reported.