Spin-forbidden c3Σ1+←X1Σ+ band system of YF

Optical spectra of jet-cooled diatomic YF have been recorded using resonant two-photon ionization spectroscopy. A vibrational progression corresponding to the c (3)Sigma(+)(1)<- X (1)Sigma(+) system has been identified. The vibrational frequency omega(')(e) and anharmonicity omega(')(e)x(e)(') of the c (3)Sigma(+) state are 546.70 and 2.45 cm(-1), respectively. The 0-0, 1-0, and 2-0 bands of the c (3)Sigma(+)(1)<- X (1)Sigma(+) system were rotationally resolved and analyzed, allowing the v(')=0, 1, and 2 levels of the c (3)Sigma(+)(1) substate to be characterized. From these studies, B-e(')=0.269 81(3) cm(-1), alpha(')(e)=0.001 72(3) cm(-1), and r(e)(')=1.9979(1) A were obtained (1 sigma error limits). For these levels the spin-spin coupling constant lambda(v) is identical within experimental error, as lambda=-22.5 cm(-1). The spin-forbidden c (3)Sigma(+)(1)<- X (1)Sigma(+) transition is made allowed by spin-orbit interaction between the c (3)Sigma(+)(1) and the B (1)Pi states. Excited state lifetimes of the c (3)Sigma(+)(1) and the B (1)Pi states have been measured as 7.11(41) and 0.133(15) mu s, respectively. A spin-orbit analysis shows that the c (3)Sigma(+)(1) state is contaminated with 2% B (1)Pi character, which is approximately sufficient to explain the 7 mu s lifetime of the c (3)Sigma(+)(1) state. (c) 2007 American Institute of Physics.