Understanding temporal evolution of diatomic rovibrational molecular spectra of BO molecule

Boron, a well-known element in analytical and technical industry especially in nuclear industry. Due to its high neutron absorption cross-section, several purposes arises for the use of natural and enriched boron materials. Laser Ablation Molecular Isotopic Spectroscopy (LAMIS) is one of the distinct method for real time analysis of isotopic ratio. The higher isotopic shift in the boron oxide emission band (0.73 nm) draws attention to this method since the isotope splitting of boron atomic lines (0.0025 nm) is comparatively small. In the present study, the temporal evolution of rotational-vibrational (ro-vibrational) bands of B²Ʃ⁺ → X²Ʃ⁺ (B-X) transition was analysed for the diatomic boron oxide molecule using boric acid pellets. The B-X transition is primarily observed in UV region (~220-330 nm) and the band origins were calculated using the diatomic constants reported by Mélen et.al. The temporal analysis of these BO bands were carried out by varying the acquisition delay time (t_d) from 0.2 μs to 15 μs and gate width (t_w) were kept same as that of t_d. The data was normalized by t_w. Along with BO molecular emission, temporal evolution of boron atomic and ionic lines, B(I)261.35 nm, B(II)345.13 nm and B(III)247.9 nm were also studied. The study gives an idea about the time dependent influence of atomic and ionic species in molecular information of B-X transition of boron oxide. The (0-2) vibrational band showed better intensity and less spectral interference. The study shows, that the (0-2) band is the best choice for boron isotopic ratio calculation using LAMIS technique