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Abstract: A single band belonging to the band system has been rotationally analyzed for each of the two isotopologues, BaOH and BaOD, using high-resolution V-type optical–optical double resonance spectroscopy. BaOH and BaOD molecules were synthesized in a Broida-type oven. High-resolution spectra were recorded by monitoring the dip in fluorescence of the transition excited by a single-mode ring dye laser (pump laser), whilst a single-mode Ti:Sapphire laser scanned the corresponding transition. The observed spectra resemble a typical transition, believed to emanate from single or triple quanta of the bending vibration in the state. Measured rotational lines have been assigned and rotational and fine structure parameters determined through a combined least-squares fit with the millimeter-wave pure rotational data of the state. Previous analyses of the transitions of BaOH and BaOD yielded significantly different spin–orbit coupling constants, which were attributed to possible global and local perturbations arising from vibrationally-excited bands of the state. Although the newly observed state bands have not been conclusively assigned a specific spin state, the derived Ω-doubling constants show significant character, further indicating strong interactions between the and states of BaOH. To validate these conclusions, ab initio calculations have been carried out to further understand the nature of the BaOH excited states. The , , , , , and states have been characterized by means of multireference configuration interaction calculations using the MOLPRO software. Calculated vertical term energies show relatively good agreement with existing optical data. [Copyright &y& Elsevier]

Abstract: The transition of BaOD has been rotationally analyzed using laser excitation spectroscopy. BaOD molecules were synthesized through the reaction of Ba atoms with D2O in a Broida-type oven. Rotational and fine structure parameters determined for the state of BaOD yielded a spin-orbit coupling constant A significantly different from the corresponding value for BaOH (∼605.8cm−1 versus 560.1cm−1). Λ-doubling constants for the state were observed to be in poor agreement with the predictions of the pure precession model for the interaction between the and the states in BaOD. Explanations for the unusual spin-orbit splitting and apparent failure of the pure precession and unique perturber models in BaOH and BaOD are discussed, with particular reference to possible global and local perturbations arising from vibrationally excited bands of the state. [Copyright &y& Elsevier]

Abstract: The high-resolution spectrum of the transition of BaOH has been recorded using laser excitation spectroscopy. The BaOH molecules were synthesized through the reaction of Ba atoms with H2O2 in a Broida-type oven. Rotational and fine structure parameters have been determined for the state through a combined least-squares fit with the millimeter-wave pure rotational data of the state. The Λ-doubling constants observed for the state are in poor agreement with the predictions of the pure precession model of the interactions between the and the states of BaOH. In addition to the bands of the transition, three bands located at ∼11443cm−1, ∼12013cm−1 and ∼12505cm−1, respectively, were also observed and analyzed but their vibrational and electronic assignments are not clear. Possible assignments of the three unidentified bands are discussed based on the derived spectroscopic constants and the vibrational assignments of previous low-resolution work. [Copyright &y& Elsevier]

Abstract: The and states of SrOH were investigated using optical–optical double-resonance (OODR) spectroscopy. Rotational and fine structure parameters have been determined for these two states through a combined least-squares fit of the current OODR data along with the OODR data of the transition, the optical data of the transition and the millimeter-wave pure rotational measurements of the state. The spin–rotation constant, γ, of the state was found to be 0.002653cm−1, which is two orders of magnitude smaller than that of the state (−0.1447cm−1). This small γ value suggests that this state arises from a Sr+ atomic orbital of mainly 6sσ character. This atomic orbital assignment is also supported by the large rotational constant observed in the state and the similarity of the molecular constants to those of the state of CaOH. The rotational energy levels of the state of SrOH were found to be largely perturbed, which prohibited the accurate determination of the spin–rotation constant in this state. This perturbation is most likely due to an interaction with a 2Σ vibronic component of the nearby state. [Copyright &y& Elsevier]

Abstract: Optical–optical double-resonance spectroscopy has been used to record a high-resolution spectrum of the transition of SrOH. Rotational and fine structure parameters have been determined for the state through a combined least-squares fit with the optical transition data and the millimeter-wave pure rotational data of the state. The spin-orbit constant of the state was found to be 24.6607cm−1, which is significantly smaller than in the à 2Π state. This change can be rationalized by the different atomic orbital character of the à 2Π and states. The values of the Λ-doubling constants in the state have been examined in terms of the pure procession model. The agreement between the calculated and observed Λ-doubling constants suggests that the state may form a unique perturber pair with the nearby state. [Copyright &y& Elsevier]

Abstract: The state of CaOH was investigated using optical–optical double resonance spectroscopy. A combined least-squares fit of the double resonance transition data along with optical transition data and the millimeter-wave pure rotational data of the state was performed using an effective Hamiltonian. The spin–rotation constant was determined for the state for the first time. An analysis of these constants showed that the Ca–O bond length and spin–rotation parameter of the state have the smallest values of all the observed 2Σ+ states of CaOH. This evidence suggests the assignment of the state as arising from a Ca+ atomic orbital of mainly 5sσ character. This atomic orbital assignment was shown to be consistent with both previous work on CaF and recent theoretical calculations on CaOH. [Copyright &y& Elsevier]

Abstract: The electronic transition of SrNH2 has been recorded at high resolution using laser-ablation/molecular jet techniques. Transitions arising from the and levels have been observed. The data have been analyzed using the S-reduced asymmetric top Hamiltonian to determine rotational and fine structure parameters. The spin–rotation constants of the state were calculated using the pure precession model. These values were found to be in relatively good agreement with the experimentally determined parameters, however slight differences suggest that the unpaired electron in the state is not entirely of p orbital character. A molecular structure was also determined for the state of SrNH2. The strontium–nitrogen bond was found to decrease by 0.011Å while the H–N–H bond angle was found to increase by 2.5° between the and states. A small positive inertial defect was calculated for the state, indicating that the molecule is planar. [Copyright &y& Elsevier]

Abstract: The laser-induced excitation spectrum of the transition of SrCCH has been recorded at high resolution. A rotational analysis has been performed yielding rotational and fine structure parameters for the à state. In addition, a vibrational frequency for the Sr–C stretch (ν 3) in the à 2Π state has been determined. Using the rotational constant of the à state, the Sr–C bond length was determined to be 2.43Å, which is ∼0.03Å shorter than in the ground state. A comparison of the Λ-doubling constant p, to those of the other alkaline-earth acetylides suggests that SrCCH and CaCCH appear to follow the pure precession model unlike MgCCH. Finally, a search for the transition was negative, as with CaCCH, suggesting that the state may be predissociative. [Copyright &y& Elsevier]

Abstract: The Fourier-transform infrared emission spectra of BO were recorded using a Bruker IFS 125 HR spectrometer. The observed spectrum of BO in the 1200–2100cm−1 region contains three bands: the fundamental bands of 11BO and 10BO and a hot band of 11BO with band origins measured to be 1861.9242(97), 1915.3071(09) and 1838.3773(68) cm−1, respectively. [ABSTRACT FROM AUTHOR]