Ultraviolet and Infrared Spectra of Diboron in Solid Neon at 4 K

Apart from products H, B, BH, BH₂ and BH₃ identified from their emission spectra in the UV/Vis region, photolysis of diborane(6) dispersed in solid neon at 4 K with far-ultraviolet light from a synchrotron led to observation of absorption line (0,0) of the electronic transition A ³ Σ_u^- ←X ³ Σ_g^- of B₂ at 326.39 nm. Absorption lines (1,0) of ¹¹ B₂ , ¹¹ B¹⁰ B and ¹⁰ B₂ were recorded at 316.63, 316.40 and 316.15 nm, respectively. ΔG_1/2 of state A ³ Σ_u^- for ¹¹ B₂ , ¹¹ B¹⁰ B and ¹⁰ B₂ in solid neon are accordingly derived to be 945, 968 and 993 cm^-1 , respectively. Weak lines (0,1) of ¹¹ B₂ at 29586 cm^-1 and of ¹¹ B¹⁰ B at 29560 cm^-1 , corresponding to 1042±30 and 1068±30 cm^-1 for vibrational modes in the electronic ground state, were recorded in emission. An absorption line recorded at 1066.5±0.5 cm^-1 in infrared spectra after photolysis of either B₂ H₆ in Ne or B₂ D₆ with D₂ in Ne is thus attributed to ¹¹ B¹⁰ B.