The A(1)Pi-X-1 Sigma(+) (2,0) transition in (BH)-B-11 and (BH)-B-10 observed by (1+2)-photon resonance-enhanced multiphoton ionization spectroscopy

We report the mass-selected resonance-enhanced multiphoton ionization (REMP I) spectrum of photolytically produced diatomic boron hydride over the spec tral range from 368 to 372 nm. Features recorded for time-of-flight-resolve d cation masses 12, 11 and 10 amu are assigned to the one-photon transition , A(1)II (v ' = 2)-X(1)Sigma (+) (v " = 0), in (BH)-B-11 and (BH)-B-10. Cat ion production at these wavelengths requires three photons. This signal mus t therefore reflect resonant one-photon absorption followed by two-photon i onization in a (1 + 2)-photon process. This work represents the first obser vation of the well-characterized A(1)II-X(1)Sigma (+) system in ionization spectroscopy and the first measurement of line positions in the A(1)II v = 2 state for (BH)-B-10. (C) 2001 Elsevier Science B.V. All rights reserved.