title: Spin-forbidden c 3Sigma1+<--X 1Sigma+ band system of YF.
abstract: Optical spectra of jet-cooled diatomic YF have been recorded using resonant two-photon ionization spectroscopy. A vibrational progression corresponding to the c 3Sigma1+<--X 1Sigma+ system has been identified. The vibrational frequency omegae' and anharmonicity omegae'xe' of the c 3Sigma+ state are 546.70 and 2.45 cm-1, respectively. The 0-0, 1-0, and 2-0 bands of the c 3Sigma1+<--X 1Sigma+ system were rotationally resolved and analyzed, allowing the v'=0, 1, and 2 levels of the c 3Sigma1+ substate to be characterized. From these studies, Be'=0.269 81(3) cm-1, alphae'=0.001 72(3) cm-1, and re'=1.9979(1) A were obtained (1sigma error limits). For these levels the spin-spin coupling constant lambdav is identical within experimental error, as lambda=-22.5 cm-1. The spin-forbidden c 3Sigma1+<--X 1Sigma+ transition is made allowed by spin-orbit interaction between the c 3Sigma1+ and the B 1Pi states. Excited state lifetimes of the c 3Sigma1+ and the B 1Pi states have been measured as 7.11(41) and 0.133(15) micros, respectively. A spin-orbit analysis shows that the c 3Sigma1+ state is contaminated with 2% B 1Pi character, which is approximately sufficient to explain the 7 micros lifetime of the c 3Sigma1+ state.
authors: Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.
authors: Ramya
authors: R
authors: Nagarajan
authors: Michael D
authors: MD
authors: Morse