HYPERFINE STRUCTURE OF THE $B {^{2}}\Sigma^{+} - X {^{2}}\Sigma^{+}$ TRANSITION OF LaS

Author Institution: Department of Chemistry, The University of Hong Kong; Department of Chemical Physics, University of Science and Technology of ChinaHigh-resolution spectra of the $B ^{2}\Sigma^{+} - X {^{2}}\Sigma^{+} (0,0)$ transition of LaS, near $13770 cm^{-1}$, have been observed under jet-cooled conditions, following the reaction of laser ablated lanthanum metal with $CS_{2}$. With a linewidth of about 45 MHz, the hyperfine structure of LaS is well resolved. The ground state, $X {^{2}}\Sigma^{+}$, conforms to case $b_{\beta s}$ coupling scheme, however, the upper state, $B {^{2}}\Sigma^{+}$, is more appropriate to be described by case $b_{\beta s}$ coupling scheme. Accurate molecular parameters for both the $B {^{2}}\Sigma^{+}$ and $X {^{2}}\Sigma^{+}$ will be reported