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The resonance enhanced multiphoton ionization (REMPI) spectrum of jet-cooled CS2 has been recorded in the one-photon wavelength range 460–500 nm, corresponding to the three photon excitation energy range 60 000–65 000 cm−1. A previous assignment of one photon forbidden transitions in this region to 3d Rydberg states is shown to be incorrect and reassigned to the 4pπ 1,3Δu states. In fact all the observed states in this region can be assigned to 4p Rydberg states; the 4pσ 1,3Πu states at 62 768 and 62 083 cm−1, respectively, and the 4pπ 1,3Δu states at 64 214 and 63 698 cm−1, respectively. Another band at 64 374 cm−1 may be due to a three photon excitation to the 4pπ 1Σ+u Rydberg state. Our resolution is sufficient to resolve band shapes enabling symmetry assignments when coupled with their polarization behavior. The fact that the origin bands are not degraded and that Δν=0 sequence bands are strongly excited whereas Δν≠0 transitions are either absent or very weak implies that the upper states have a linear geometry similar to that of the ground state. A comparison of singlet–triplet splittings suggests the 4pπ Δu states have stronger Hund’s case (c) character than the 4pσ Πu state. While CS+2 was generally the predominant ion formed, resonance ionization through the 1Δu←X 1Σ+g origin band led to an unusual predominance of S+ and CS+ ions. This is explained by multiphoton fragmentation of CS+2 via an accidental one-photon resonance from the X 2Π1/2 (v=0) ionic ground state.

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UV photoelectron spectra have been recorded for the F + NH20H reaction at different reaction times. At short reaction times three bands associated with NH,O were observed, whereas at longer reaction times one band associated with NHO was seen.The NH20 bands were assigned with the aid of ab initio molecular orbital calculations which used an essentially planar equilibrium geometry for the neutral ground state. The HNO band showed resolved vibrational structure which was analysed in terms of excitation of the N-0 stretching and HNO deformation modes in HNO+(g 2A'). The first adiabatic and vertical ionization energies of HNO(g 'A') were measured as 10.18 & 0.01 and 10.56 0.01 eV, respectively. Assignment of the vibrational structure was confirmed by recording the first photoelectron band of DNO, prepared from the F + ND20D reaction.

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The (1+1′)+1 resonance enhanced multiphoton ionization (REMPI) spectrum of jet-cooled CS2 has been recorded in the 61 000–65 600 cm−1 excitation energy range. Four prominent band groups are observed that can be assigned to Δν2=−1 and Δν2=1 sequences of the two-photon electronically forbidden 4p 1,3Δu←X̃ 1Σ+g transitions. Weak bands to higher energy appear to be associated with the 310, 230 and 110210 bands and corresponding sequence bands. The results show that the upper states are not 3d Rydberg states as has been previously supposed, and are consistent with a recent reinvestigation of the corresponding (3+1) REMPI spectrum. Further experimental information is obtained on the anomalous vibrational band structure of transitions to the 3Δu state. The 201 and 212 bands of the 4p 1Πu←X̃ 1Σ+g transition are also observed, but are much weaker, suggesting that vibronic interactions are less important in this state compared to the 4p 1,3Δu states.

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