Reinvestigation of the electronic transition moment function of the BO B2Σ+-X2Σ+ band system

- Relative intensities of 9 emission bands of the BO B-X system are measured.
- Some bands are measured for the first time in this work.
- Radiative transition parameters for the BO B-X system are computed.
- Measured and computed band intensities are reconciled with standard theory.
- Absolute electronic transition moment function is derived for BO B-X.

The relative intensities of nine emission bands associated with the v′=0 and 1 vibrational levels of the B2Σ+-X2Σ+ system of the BO molecule are measured. The integrated relative intensities of the (0, 0), (0, 1), (1, 0) and (1, 1) bands are measured for the first time in this work. The ratios of observed intensities for bands originating from the same upper vibrational level, together with the Franck-Condon factors, qv′v″, and r-centroids, r¯v′v″, based on Rydberg-Klein-Rees potential energy curves, derived from the best available spectroscopic data for the B2Σ+ and X2Σ+ states of 11B16O and 10B16O, are used to reinvestigate the dependence of the electronic transition moment (ETMF), Re(r), on internuclear distance, r, for the BO B2Σ+-X2Σ+ band system. The linear expression Re(r¯v′v″)=k(−1+1.393r¯v′v″), where k is an arbitrary constant, is derived from our data to describe the measured r-centroid variation of the ETMF for this system over the range 1.23Å≤r≤1.40Å of internuclear distance. The form of this expression is suitable for directly comparing with previous work, and we find excellent agreement with the BO B-X relative ETMF of Robinson and Nicholls [Intensity measurements on the CO+ comet tail, and the BO α and β molecular band systems. Proc. Phys. Soc. 1960;75:817-25]. Recent radiative-lifetime measurements of the 11BO B state have allowed us to normalize our ETMF to absolute units: Re(r¯v′v″)=0.4672r¯v′v″−0.3354 (electric dipole moment atomic units), where r¯v′v″ is in Å.