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Two-photon absorption spectroscopy with a mass-selected beam of CO+2 ions was used to study the predissociative C 2Σ+g state of CO+2. The first photon pumped the A 2Πu←X 2Πg transition and the second photon was used to scan through the C 2Σ+g←A 2Πu transition. A rotational analysis of two bands in this spectrum has been made. The C 2Σ+g state is linear with a C–O bond length of 1.1552(2) Å in the v=0 level. [ABSTRACT FROM AUTHOR]

A technique for the spectroscopic characterization of mass-selected ions in ground and bound excited electronic states involving two-photon absorption and fragment ion detection is demonstrated. A triple quadrupole mass analyzer system is used. Collisionally relaxed ions (M+) from a high pressure source are mass selected, then excited sequentially by two laser colors (λ1,λ2) according to M+→λ1M+*→λ2M+**→F+i and fragment ions (F+i) are detected. Stable ionic states are characterized by scanning λ1 with constant λ2 and this is illustrated on the known transitions of N2O+ (A 2Σ+←X 2Π) and of CS+2 (B 2Σ+u←X 2Πg). New spectroscopic information—vibrational frequencies and rotational constants—and dynamic parameters—lifetimes and fragmentation branching ratios—on N2O+(B 2Σ+) and CS+2 (C 2Σ+g) are obtained by scanning λ2 when λ1 is chosen to populate several or individual rotational levels of the intermediate state. [ABSTRACT FROM AUTHOR]