Study of the A1Π→X1Σ+ Bands of B11F with a Vacuum Echelle Spectrograph

The A¹Π→X¹Σ⁺ bands of B¹¹F which had been found by Chrétien and Miescher were now studied with the aid of a higher dispersion spectrograph and more accurate molecular constants were obtained, i.e., $A^1{\mathrm{\Pi :T}}_e{\text{=51\hspace{0.17em}157.4}}_8\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\omega }}_e{\text{=1264}}_{\text{.96}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\omega }}_e{x}_e{\text{=12.5}}_3\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\omega }}_e{y}_e{\text{=−0.24}}_2\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,B}}_e{\text{=(c)1.420}}_5\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\text{,(d)1.420}}_7\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\alpha }}_e{\text{=0.016}}_5\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\gamma }}_e{\text{=−0.0005}}_7\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\text{,D=7×10}}^{\text{−6}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,r}}_e{\text{=1.304}}_7{\mathrm{A;X}}^1{\Sigma }^{+}{\mathrm{:\omega }}_e{\text{=1402.1}}_3\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\omega }}_e{x}_e{\text{=11.8}}_4\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\omega }}_e{y}_e{\text{=+0.05}}_6\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,B}}_e{\text{=1.510}}_7\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\alpha }}_e{\text{=0.016}}_5\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\gamma }}_e{\text{=−0.0001}}_5\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\text{,D=7×10}}^{\text{−6}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}{\mathrm{,r}}_e{\text{=1.265}}_{2}A$ . Λ‐type doubling was observed in the A¹Π state, and a brief discussion of the doubling is given in this report.