Photodissociation spectroscopy of Ca+–H2O and Ca+–D2O

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Abstract
Electronic spectra are observed for the monosolvated metal cation complexes Ca+–H2O and Ca+–D2O using resonance enhanced photodissociationspectroscopy. The clusters are produced in a laser vaporization/supersonic expansion source and the mass‐analyzed product is observed using a time‐of‐flight mass spectrometer. Both Ca+ and CaOH+ (or CaOD+) dissociation channels are observed on sharp resonances. Transitions from the ground electronic state to two excited electronic states are assigned, with vibrational progressions in the Ca–OH2 stretching mode. Spectroscopic constants are Ca+–H2O: (2) 2 B 2←X 2 A 1 (T 0=21 464 cm−1, ΔG 1/2=357.9 cm−1) and (2) 2 B 1←X 2 A 1 (T 0=23 273 cm−1, ΔG 1/2=335.9 cm−1); and Ca+–D2O: (2) 2 B 2←X 2 A 1 (T 0=21 447 cm−1, ΔG 1/2=350.9 cm−1) and (2) 2 B 1←X 2 A 1 (T 0=23 261 cm−1, ΔG 1/2=324.1 cm−1). These transitions are rotationally resolved, confirming the structure of the complex to be C 2v . The Ca+–H2O bond distance is 2.22 Å and the H–O–H bond angle is 106.8° in the ground state. Comparisons with theoretical calculations are also made.