Laser and Fourier Transform Spectroscopy of Gas Phase Molecules.

Laser and Fourier transform spectroscopy were used to study a variety of gas phase molecules. A series of calcium and strontium monoalkoxides, CaOR and SrOR (R=H, CH_3, CH _2CH_3, CH(CH _3)_2, CH_2CH _2CH_3, CH _2(CH_2)_2 CH_3, CH_2 (CH_3)CH_2 CH_3 and C(CH_3) _3) was studied by laser induced fluorescence and laser excitation techniques. The A - X and B - X electronic transitions were recorded. Calcium and strontium monocyclopentadienide, CaCp and SrCp, were produced in a Broida oven and the spectra were recorded at low resolution by laser techniques. The geometry of these molecules is like an "open-faced sandwich", with C_{rm 5v} symmetry. The A^2Pi - X ^2Sigma^{+} and B ^2Sigma^{+} - X^2Sigma^{+} transitions of calcium and strontium monoisocyanate, CaNCO and SrNCO, were recorded for the first time. The spectra are interpreted as arising from a molecule with linear, ionic Sr^{+}- ^{-}NCO structure. The 0-0 band of the A - X transition of SrNCO was recorded at high resolution and rotationally analyzed. The use of a 0.64 m monochromator, acting as a narrow bandpass filter, was necessary for recording the spectra and enabled the correct assignment of the rotational lines. By comparing the molecular constants of SrNCO with related molecules, the NCO^{-} ligand was found to be nitrogen bonding to the strontium atom. The Sr-N bond length was estimated to be 2.26 A in the ground state. The rotational analysis of the 0-0 band of the A^2E_{1/2} - X^2A_1 transition of the SrOCH_3 free radical has been carried out by laser excitation spectroscopy. The SrOCH_3 molecule was found to have C_{rm 3v} symmetry with a Sr-O bond length of 2.12 A. There was no evidence of a Jahn-Teller effect in the A^2E state. This work is the first high-resolution analysis of a metal alkoxide molecule. The rotationally cool (30 K) spectrum of the 0 -0 vibrational band of the A^2Delta - X^2Pi electronic transition for the diatomic free radical CCl was recorded using a Fourier transform spectrometer. The first rotational lines of the six strongest branches were observed, and transitions in three other branches were also detected. The CCl radical was produced in a corona-excited supersonic expansion source.