Rotationally Resolved Vacuum Ultraviolet Laser Spectra of the37Cl211Σ+u←X1Σ+gTransition

• Published in: Journal of molecular spectroscopy 1998-08, Vol.190 (2), p.213-225
• Main Authors: Wang, P., Okuda, I.V., Dimov, S.S., Lipson, R.H.
• Format: Article
• Language: English
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1006/jmsp.1998.7558

Rotationally and isotopically resolved single-photon excitation spectra of jet-cooled Cl2in the wavelength region between 133 and 138 nm were recorded using a tunable vacuum ultraviolet “laser” generated by two-photon resonantly enhanced four-wave difference mixing in Kr gas. The dominant transition (11Σ+u←X1Σ+g) is well known theoretically and experimentally to involve a double-well excited state potential energy curve formed by a strong homogeneous Rydberg-state/ion-pair state avoided crossing. In this work, single isotopomer spectra were obtained by dispersing and detecting ions produced by (1 + 1′) resonance-enhanced multiphoton ionization in a time-of-flight mass spectrometer. In this way, rotational constants were deduced for the first time for many v′ levels of the least abundant molecular isotope,37Cl2, which are both localized in the Rydberg well, and delocalized in the ion-pair portion of the 1-state potential energy curve. Our experimentally derived band origins andB′vvalues test the practical validity of an analytical 11Σ+upotential energy function which is a modified version of the one first proposed by J. Wörmer, T. Möller, J. Stapelfeldt, G. Zimmerer, D. Haaks, S. Kampf, J. Le Calvé, and M. C. Castex (1988. Z. Phys. D,7,383–395).