Molecular Constants for the v=0, b(1)Sigma(g)(+) Excited State of O(2): Improved Values Derived from Measurements of the Oxygen A-Band Using Intracavity Laser Spectroscopy

The spin-forbidden a 4Σ--X 2Π1/2 transition of GeH detected in absorption using intracavity laser spectroscopy

The a ⁴Σ^--X ²Π_1/2 transition of GeH has been recorded in absorption for the first time using Intracavity Laser Spectroscopy (ILS). The GeH molecules were produced in a 0.40-0.60 A DC plasma discharge inside an aluminum hollow cathode, using 500 mTorr of Ar, 100 mTorr of H₂, and 200 mTorr of GeH₄. This cathode is located within the resonator cavity of a Coherent Verdi™ V-10 pumped dye laser. Effective path lengths for this series of measurements using the ILS method ranged from 2 to 7 km. Spectra were calibrated using the absorption spectrum of I₂ collected from an extracavity cell, the I₂ transmission spectrum from Salami and Ross, J. Mol. Spectrosc. 223(1), 157 (2005) and PGOPHER's [C. M. Western, J. Quant. Spectrosc. Radiat. Transfer 186, 221-242 (2016)] calibration feature. Differences in peak positions between calibrated experimental spectra and the reference data were on average less than ±0.002 cm^-1. All eight branches expected to have appreciable intensity for the transition have been identified, and isotopologue splitting was observed in features of 5 of the 8 identified rotational branches. Molecular constants have been obtained for the a ⁴Σ^- states of ⁷⁰GeH (20.84% abundant), ⁷²GeH (27.54% abundant), and ⁷⁴GeH (36.28% abundant). The transitions were fit using PGOPHER, holding the ground state constants fixed to the values reported by Towle and Brown [Mol. Phys. 78(2), 249 (1993)]. The constants for the a ⁴Σ^- state of ⁷⁴GeH determined by the fit are T₀ = 16 751.5524(13) cm^-1, B₀ = 6.764 912(33) cm^-1, D₀ = 0.459 60(17) × 10^-3 cm^-1, λ_SS = 9.7453(12) cm^-1, λ_D = 0.468(14) × 10^-3 cm^-1, γ = 0.077 878(84), and γ_S = -0.361(77) × 10^-3 cm^-1.

High resolution electronic spectroscopy of the A (2)Σ- - X (2)Π1/2 transition of PtN

The (2,0) vibrational band of the A (2)Σ(-) - X (2)Π1/2 transition of platinum nitride, PtN, was recorded at Doppler-limited resolution using intracavity laser absorption spectroscopy (ILS) and at sub-Doppler resolution using molecular beam laser induced fluorescence (LIF) spectroscopy. Isotopologue structure for (194)PtN, (195)PtN, and (196)PtN, magnetic hyperfine splitting due to (195)Pt (I = ½), and nuclear quadrupole splitting due to (14)N (I = 1) were observed in the spectrum. Molecular constants for the ground and excited states are derived. The hyperfine interactions are used to illuminate the nature of the A (2)Σ(-) excited electronic state.

Photoelectron Imaging Study of the Effect of Monohydration on O2- Photodetachment

The photodetachment of the O(2)(-).H(2)O cluster anion at 780 and 390 nm is investigated in comparison with O(2)(-) using photoelectron imaging spectroscopy. Despite the pronounced shift in the photoelectron spectra, the monohydration has little effect on the photoelectron angular distributions: for a given wavelength and electron kinetic energy (eKE) range, the O(2)(-).H(2)O angular distributions are quantitatively similar to those for bare O(2)(-). This observation confirms that the excess electron in O(2)(-).H(2)O retains the overall character of the 2ppi(g) HOMO of O(2)(-). The presence of H(2)O does not affect significantly the partial wave composition of the photodetached electrons at a given eKE. An exception is observed for slow electrons, where O(2)(-).H(2)O exhibits a faster rise in the photodetachment signal with increasing eKE, as compared to O(2)(-). The possible causes of this anomaly are (i) the long-range charge-dipole interaction between the departing electron and the neutral O(2).H(2)O skeleton affecting the slow-electron dynamics; and (ii) the s wave contributions to the photodetachment, which are dipole-forbidden for pi(g)(-1) transitions in O(2)(-), but formally allowed in O(2)(-).H(2)O due to lower symmetry of the cluster anion and the corresponding HOMO.