Pure rotational spectra of PbSe and PbTe: potential function, Born–Oppenheimer breakdown, field shift effect and magnetic shielding

Abstract

The pure rotational spectra of 41 isotopic species of PbSe and PbTe have been measured in their X 1Sigma+ electronic state with a resonator pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of suitable target rods and stabilised in supersonic jets of noble gas. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients delta01 for Pb, Se and Te. Unusual large values of the BOB parameters for Pb have been rationalized in terms of finite nuclear size (field shift) effect. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both PbSe and PbTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 207Pb, 77Se, 123Te, and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.

Rotational spectra, potential function, Born–Oppenheimer breakdown and magnetic shielding of SiSe and SiTe

“…An example of the typical hyperfine structure pattern is given in Fig. 1, which displays the J = 2 1 transition of 28 Si 77 Se: besides the strong DF = DJ = + 1 doublet, the weaker DF = 0 hyperfine component is also visible. The hyperfine analysis was performed independently for each isotopologue using Pickett's SPFIT program [17], yielding its ground-state rotational constant B 0 , quartic centrifugal distortion constant D 0 , and the nuclear spinrotation coupling constant C I of the relevant nucleus.…”

“…(14b). The most recent literature values of x e and Àx e x e derived from electronic spectroscopy for the parent species 28 Si 80 Se [8] and 28 Si 130 Te [10] are also included in Table 5 for comparison. The present DPF analysis of the SiSe and SiTe rotational data were performed keeping the dissociation energies D e constrained to the theoretically computed values of Refs.…”

“…The analyses reported here for SiSe and SiTe were performed using LeRoy's DPOTFIT 1.1 programme [27], and using the same model successfully employed for the DPF of the spectroscopic data of tin [15] and lead chalcogenides [28]: V ð1Þ ad ðrÞ is the ''extended Morse oscillator" EMO 1 (3,3) potential function…”

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

“…30). Therefore, the fitted BOB parameter for PbI is most likely representing a field-shift effect as noted by Tiemann et al and Giuliano et al and has been seen before in lead containing compounds (e.g., PbSe and PbTe 35,36 ). As there is only one isotope for iodine, a more robust analysis is not possible.…”

Vibrational energies and full analytic potential energy functions of PbI and InI from pure microwave data

“…The conditions employed are apparently particularly favourable to the generation of excited vibrational states of PbI and InI. Excited vibrational states are commonly observed in spectra recorded for molecules generated through a combination of laser vaporization and supersonic expansion [20][21][22][23].…”