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The energy region just above the first dissociation limit in SO is investigated by a combination of jet cooled 1+1 multiphoton ionization spectroscopy and ab initio calculations. Two electronic states, the C 3Π and d 1Π states, are found to give sharp, rotationally resolved spectra, and a complete analysis of these is presented for the first time. The potential energy curve for the d 1Π is found to be unusual, with only four bound levels and a maximum that does not correspond to a conventional avoided crossing. Our assignments are supported by ab initio calculations, which also predict the interactions between electronic states from spin–orbit coupling. Experimental evidence for these, in the form of perturbations in the observed spectra and predissociation is discussed. Based on our ab initio calculations we also reassign some previous observations to the e 1Π state.

Radiative and predissociative lifetimes of the A 2 Σ + state (v ′ =0,1) of SH and SD: A highly correlated theoretical investigation A theoretical characterization of the quartet states of the SO + molecular ion Intersystem crossing rate constants from the (0,4,1) and (1,2,1) levels of the à 1 A 2 to ã 3 B 1 state of SO 2 Laser induced fluorescence and 1ϩ1 resonance enhanced multiphoton ionisation spectra of the A 3 ⌸ -X 3 ⌺ Ϫ transition of SO radicals prepared by an electric discharge in a supersonic jet expansion are presented. Rotational constants are given for A state vibrational levels with vЈ ϭ0 -13, extending to within 190 cm Ϫ1 of the A state dissociation limit. The Rydberg-Klein-Rees curve derived from these constants shows significant anharmonicity, even around the equilibrium geometry. In addition, several small local perturbations of the rotational structure are observed. Collision free fluorescence lifetimes are determined for the complete range of vibrational states, and are found to fall smoothly from 29.5 s for vЈϭ0 to 6.45 s for vЈϭ12. Combining these data with earlier measurements leads to a better determination of the A -X transition dipole moment over the range 1.4-2.0 Å.

We describe the construction of an all solid-state, narrow bandwidth, pulsed optical parametric oscillator (OPO) based on ß-barium borate nonlinear crystals. The OPO was injection seeded by an external cavity diode laser in the range 755–855 nm to generate high power narrow bandwidth tunable light in this range and simultaneously at 606–669 nm. The bandwidth of the visible light was ~130 MHz, and after frequency doubling or sum frequency mixing with the second harmonic of the pump Nd:YAG laser, sub-Doppler spectra with an overall resolution of 450 MHz were taken in the UV. The system is demonstrated by taking high-resolution spectra of the v' = 2–3 and 5–7 bands of the A?3?–X?3S-(v',0) progression and the v' = 4–v? = 0 band of the d?1?–a?1? transition in PF. These spectra show clear hyperfine structure, and an analysis of this structure is presented and interpreted in terms of the electronic structure of the molecule. As a prelude to this high-resolution study, the first ten members of the A–X band system and the first five members of the d–a band system were recorded at the moderate resolution provided by a pulsed dye laser

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