Electronic spectra are observed for the monosolvated metal cation complexes Ca+–H2O and Ca+–D2O using resonance enhanced photodissociation spectroscopy. 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) 2B2←X 2A1 (T0=21 464 cm−1, ΔG1/2=357.9 cm−1) and (2) 2B1←X 2A1 (T0=23 273 cm−1, ΔG1/2=335.9 cm−1); and Ca+–D2O: (2) 2B2←X 2A1 (T0=21 447 cm−1, ΔG1/2=350.9 cm−1) and (2) 2B1←X 2A1 (T0=23 261 cm−1, ΔG1/2=324.1 cm−1). These transitions are rotationally resolved, confirming the structure of the complex to be C2v. 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.

A comparative study of the hyperfine interactions in the X 2Σ+ state of TiN and the X 3Δ state of TiO has been performed. The 48Ti14N(I=1) hyperfine structure was determined from the analysis of 19 components of the N=1–0 and N=2–1 pure rotational transitions recorded using the pump/probe microwave-optical double resonance technique. The 47Ti(I=5/2) hyperfine structure of X 2Σ+ TiN was determined from an analysis of the high resolution optical spectrum of the (0,0) A 2Π3/2–X 2Σ+ band system. The resulting parameters are (in MHz) B(48Ti14N)=18 589.3513(13), D(48Ti14N)=0.026 31(18), γ(48Ti14N)=−52.2070(13), bF(N)=18.480(3), c(N)=0.166(7), eQq0(N)=−1.514(8), CI(N)=0.0137(12), bF(47Ti) =−558.8(11), c(47Ti)=−15(5), and eQq0(47Ti)=62(16). An analysis of the (0,0) band of the B 3Π–X 3Δ system of 47Ti16O produced the X 3Δ hyperfine parameters (in MHz): a(47Ti) =−54.7(21), (bF+2c/3)(47Ti)=−231.6(60), and eQq0(47Ti)=−49(31). An interpretation based upon the predicted nature of the bonding in TiO and TiN is given.

The permanent electric dipole moments of CaOH and SrOH in their X 2Σ+, A 2Π3/2, A 2Π1/2, and B 2Σ+ states have been measured using the technique of supersonic molecular beam optical Stark spectroscopy. For CaOH the values obtained were μ(X 2Σ+)=1.465(61)D, μ(A 2Π1/2)=0.836(32)D, μ(A 2Π3/2)=0.766(24)D, and μ(B 2Σ+)=0.744(84)D, while for SrOH the values were μ(X 2Σ+)=1.900(14)D, μ(A 2Π1/2)=0.590(45)D, μ(A 2Π3/2)=0.424(5)D, and μ(B 2Σ+)=0.396(61)D. The results are compared with values from a recent ab initio calculation for CaOH and with the predictions of a semiempirical electrostatic polarization model.

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Electronic spectra are observed for the metal cation complex Ca+–CO2, using resonance-enhanced photodissociation spectroscopy. The complexes are produced in a laser vaporization/supersonic expansion source, size selected and excited on resonance, and the mass-analyzed product is measured in a time-of-flight mass spectrometer. Both Ca+ and CaO+ dissociation channels are observed to have sharp resonances. Spectra from two isotopomers, the 40Ca+ and 44Ca+ species, are recorded and analyzed. Transitions from the X 2Σ+(v″=0) ground vibronic state to several vibrational levels in the D 2Πr excited electronic state are measured. The structure of the complex is confirmed to be linear by the presence of prominent spin–orbit multiplets. Spectroscopic constants for the 40Ca+–CO2 complex are determined: ν00=22 099.1 cm−1, Aso′=136.3 cm−1, ωe′=258.9 cm−1, and ωexe′=4.23 cm−1.

Weakly bound complexes of the form Ca+–RG (RG=Ar, Kr, Xe) are prepared in a pulsed nozzle/laser vaporization cluster source and studied with mass-selected resonance enhanced photodissociation spectroscopy. The Ca+ (2P←2S) atomic resonance line is the chromophore giving rise to the molecular spectra in these complexes. Vibrationally resolved spectra are measured for these complexes in the corresponding 2Π←X 2Σ+ molecular electronic transition. These spectra are red shifted from the atomic resonance line, indicating that each complex is more strongly bound in its excited 2Π state than it is in the ground state. Vibronic progressions allow determination of the excited state vibrational constants: Ca+–Ar, ωe′=165 cm−1; Ca+–Kr, ωe′=149 cm−1; Ca+–Xe, ωe′=142 cm−1. Extrapolation of the excited state vibrational progressions, and combination with the known atomic asymptotes and spectral shifts, leads to determination of the ground state dissociation energies Ca+–Ar, D0″=700±100 cm−1 (0.09 eV); Ca+–Kr, D0″=1400±150 cm−1 (0.17 eV); Ca+–Xe, D0″=2300±150 cm−1 (0.29 eV). The spin–orbit splitting in the 2Π1/2,3/2 state for these complexes is larger than expected by comparison to the Ca+ atomic value.

The metal ion-complex 24Mg+–Ar has been prepared in a pulsed nozzle/laser vaporization source, mass selected with a reflection time-of-flight mass spectrometer and studied with photodissociation spectroscopy at high resolution. The (5,0) band of the A 2Πr←X 2Σ+ transition has been rotationally analyzed and the rotational constants, B″=0.1409(7) cm−1 and B′=0.1836(8) cm−1, and spin–orbit constant, A′=73.94(2) cm−1, have been determined. The bond distances in the ground and excited states of the complex (r0″=2.88 Å, r5′=2.52 Å) compare well with the values predicted by theory, and they confirm the suspected nature of the electrostatic bonding in this system.

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