Andrew J. Marr

Experimental and theoretical studies of the near-infrared spectrum of bromomethylene

New measurements in the A 1A″–X 1A′ band system of monobromomethylene (HCBr) at near-infrared wavelengths are reported. Rotationally resolved spectra of HCBr and DCBr for both naturally occurring Br isotopes are analyzed and provide accurate energies for the low-lying bending vibrational levels in both the A and X states. The experimental results are compared to extensive ab initio calculations of these two states and the low-lying a 3A″ state. The ab initio T00 value for the A–X system is calculated within 500 cm−1 of the experimental results. For the triplet state, T00 (α–X) was calculated to be 1833 cm−1. The measurements of the bending intervals in the X 1A′ state suggest that this is about 250 cm−1 too low. With this shift and inclusion of spin–orbit coupling between the a and X states, the calculated bending vibrational levels in the X state reproduce the observations, and the calculations make testable predictions of the position of the triplet and other singlet state vibronic levels. Combi...

Dipole moments and hyperfine interactions in scandium monosulfide, ScS

A supersonic molecular beam of scandium monosulfide (ScS), produced using a laser ablation/reaction source, was interrogated by laser induced fluorescence. The fine and magnetic hyperfine interactions in the (0,0) B 2Σ+–X 2Σ+ band system (origin=12 940.402 cm−1) were analyzed. The magnitude of the Stark effect was measured for the (RR24+RQ24)(0) and (PP13+PQ23)(1) branch features, giving dipole moments of μ(B 2Σ+)=5.60±0.04 D and μ(X 2Σ+)=5.64±0.04 D. The spectroscopic parameters and dipole moments are used to develop a molecular orbital bonding model and are compared with the isovalent molecules ScO and ScNH.

Detection and characterization of scandium imide, ScNH

A supersonic molecular beam of scandium imide, ScNH, and deuterated imide, ScND, were produced using a laser ablation/reaction source and interrogated by laser induced fluorescence and dispersed fluorescence spectroscopy. The field free fine and magnetic hyperfine interactions and Stark effect in the (0,0) A 2Πr–X2Σ+ transition of ScNH (origin=15 023.033 cm−1) were analyzed. Ground state vibrational spacing for ScNH and ScND was measured. The determined permanent electric dipole moments are μ(A 2Π)=4.08(7)D and μ(X 2Σ+)=2.28(15)D. Plausible molecular orbital descriptions are given for the A 2Πr and X 2Σ+ states based upon the interpretation of the spectroscopic parameters and a comparison with other isovalent molecules is made.

Hot band spectroscopy of DCBr near 0.96 μm

High resolution measurements of the 20 2 (bending) hot band of the A1A′ band system of deuterobromomethylene between 10 290cm−1 and 10 540cm−1 are described. The spectra were recorded by direct absorption of a continuous-wave frequency-modulated external cavity diode laser following pulsed ultraviolet laser photolysis of deuterated bromoform. Although the bending vibrational spacings in the A1A′ state are not regular, the rotational structure in its (020) level was found to be unperturbed at the accuracy of the experimental measurements. This observation provides strong evidence that the position of the excited triplet A3 A″, state lies to higher energy, at least 1637cm−1 above the zero point level of the ground state.