Mass-independent Dunham analysis of the known electronic states of platinum sulfide, PtS, and analysis of the electronic field-shift effect

Several new vibrational bands of the [12.5] Ω = 0⁺-X³Σ^- _Ω=0⁺ and the [15.9] B Ω = 0⁺-X³Σ^- _Ω=0⁺ transitions have been observed in high resolution absorption measurements recorded using Intracavity Laser Spectroscopy (ILS). These new bands have been rotationally analyzed and incorporated into a comprehensive PtS dataset that was fit to a mass-independent Dunham expression using PGOPHER. The comprehensive dataset included all reported field-free, gas phase spectroscopic data for PtS, including 32 Fourier transform microwave transitions (estimated accuracy: 1 kHz), 9 microwave/optical double resonance transitions (25 kHz), 51 millimeter and submillimeter transitions (25-50 kHz), 469 molecular beam-laser induced fluorescence transitions (0.003 cm^-1), and 4870 ILS transitions (0.005 cm^-1). The determined equilibrium constants have been used with the Rydberg-Klein-Rees method to produce potential energy curves for the four known electronic states of PtS. Isotopic shifts in electronic transition energy beyond expectations from the Born-Oppenheimer approximation were observed and treated as electronic field-shift effects due to the difference in the nuclear charge radius between Pt isotopes. The magnitude and sign of the determined field-shift parameters are rationalized through the analysis of the previously reported ab initio calculations.

Theoretical analysis of NMR shieldings in XSe and XTe (X = Si, Ge, Sn and Pb): the spin-rotation constant saga

How the electronic contribution to the spin-rotation constant is close to the paramagnetic contribution of the NMR absolute shielding constant?

The pure rotational spectra of the open-shell diatomic molecules PbI and SnI

Pure rotational spectra of the ground electronic states of lead monoiodide and tin monoiodide have been measured using a chirped pulsed Fourier transform microwave spectrometer over the 7-18.5 GHz region for the first time. Each of PbI and SnI has a X (2)Π1/2 ground electronic state and may have a hyperfine structure that aids the determination of the electron electric dipole moment. For each species, pure rotational transitions of a number of different isotopologues and their excited vibrational states have been assigned and fitted. A multi-isotopologue Dunham-type analysis was carried out on both species producing values for Y01, Y02, Y11, and Y21, along with Λ-doubling constants, magnetic hyperfine constants and nuclear quadrupole coupling constants. The Born-Oppenheimer breakdown parameters for Pb have been evaluated and the parameter rationalized in terms of finite nuclear field effects. Analysis of the bond lengths and hyperfine interaction indicates that the bonding in both PbI and SnI is ionic in nature. Equilibrium bond lengths have been evaluated for both species.