DIRECT OBSERVATION OF $A^{2}\Pi_{r}$ AND $B^{2}\Sigma^{+}$ IN NaNe VIA LASER INDUCED FLUORESCENCE
Loading...
Date
1978
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The Van der Waals molecule NaHe produced in a supersonic expansion has been studied with a single-mode dye laser. Excitation spectra of $A^{2} \Pi_{r} \leftarrow X^{2} \Sigma^{+}$ and $B^{2} \Sigma^{+} \leftarrow X^{2}\Sigma^{+}$ transitions were obtained by monitoring the total laser-induced fluorescence. The analysis of the spectra was performed using the classical, technique of combination differences, and the vibrational numbering of the $A^{2} \Pi_{r}$ state was determined from isotope shifts. The $v_{\Pi} = 3,4,5$, and 6 vibrational levels of the $A^{2} \Pi_{r}$ state have been observed. The spin orbit constant $A_{\Pi}$ varies from $12.109\, cm^{-1}, 11.968\,cm^{-1}$ for $v_{\Pi} = 2,3,4$ to $15,379 cm^{-1}$ for $v_{\Pi} = 6$. The lower vibrational levels are close to the theoretical Hund’s case ``a” value $11.464 cm^{-1}$ and are well described by a Hand’s case ``a” basic set. Higher vibrational levels tend to approach Hund’s case ``c” because of strong interaction with the $B^{2} \Sigma^{+}$ state. The observed $B^{2} \Sigma^{+}$ level is best described by a core ``c” basic set; however, it is not known if the single, observed $B^{2} \Sigma^{+}$ level is the lowest vibrational level. An upper limit on the repulsive part of the $B^{2} \Sigma^{+}$ potential can be obtained from the observed $\Lambda$ doubling of the $A \Pi_{1/2}, v_{\Pi} = 3,4$ levels. The long range analysis of the $A^{2}\Pi$ potential is complicated by the $A^{2}\Pi - B^{2} \Sigma^{+}$ interactions for high $v_{\Pi}$ levels. An extended analysis of higher $v_{\Pi}$ levels, where a Hund’s case ``c” basic set is applicable, is now in progress.
Description
This work is supported by the National Science Foundation Contract PHY-77-09155.
Author Institution: Massachusetts Institute of Technology
Author Institution: Massachusetts Institute of Technology