Born Oppenheimer Breakdown Parameters Research Articles

Rotational spectroscopy of rare iron monoxide isotopologues: A mass-independent analysis

We present pure rotational transitions of the rare iron monoxide isotopologues. , and in their lowest spin states . For , the rotational spectrum reveals hyperfine splitting due to the nuclear spin of . We use Dunham-like parameters to analyse the new laboratory data together with data from the literature. In particular, we are able to derive the Born–Oppenheimer breakdown parameters and and the corresponding equilibrium bond length of . With these new accurate molecular parameters line positions on a sub-MHz accuracy level can be calculated, including those of the radioactive isotopologue . The new data allow for an astronomical search for the rare isotopologues using sensitive radio telescopes, like the Atacama Large Millimetre/submillimetre Array.

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.

Quantum-chemical determination of Born–Oppenheimer breakdown parameters for rotational constants: the open-shell species CN, CO+ and BO

The quantum-chemical protocol for computing Born–Oppenheimer breakdown corrections to rotational constants in the case of diatomic molecules is extended to open-shell species. The deviation from the Born–Oppenheimer equilibrium rotational constant is obtained by considering three contributions: the adiabatic correction to the equilibrium bond distance, the electronic contribution to the moment of inertia requiring the computation of the rotational g-tensor, and the so-called Dunham correction. Values for the Born–Oppenheimer breakdown parameters of CN, CO+, and BO in their 2Σ+ electronic ground states are reported based on coupled-cluster calculations of the involved quantities and compared to available experimental data.

Quantum-chemical calculation of Born–Oppenheimer breakdown parameters to rotational constants

The paper describes how Born–Oppenheimer breakdown parameters for the rotational constants of diatomic molecules can be determined via quantum-chemical computations. The deviations from the Born–Oppenheimer equilibrium values are accounted for by considering the adiabatic correction to the equilibrium bond distances, the electronic contribution to the rotational constant via the rotational g tensor, and the so-called Dunham correction, which can be computed directly from a polynomial expansion of the potential curve around the equilibrium distance. Calculations for HCl, SiS, and HF demonstrate the accuracy that can be achieved in the theoretical treatment of the considered Born–Oppenheimer breakdown parameters and the usefulness of such calculations is illustrated for highly accurate spectroscopic measurements in the field of rotational spectroscopy.

Fourier transform microwave spectrum of and Born–Oppenheimer breakdown effects in tungsten monoxide, WOThis article is part of a Special Issue on Spectroscopy at the University of New Brunswick in honour of Colan Linton and Ron Lees.Dedicated to Ronald M. Lees and Colan Linton, in recognition of their outstanding contributions to science.

Rotational transitions of eight isotopomers of tungsten monoxide, WO, in its X0+ ground electronic state, have been measured in the frequency range 22–26 GHz, using a cavity Fourier transform microwave spectrometer. The samples were prepared by laser ablation of W metal in the presence of O2 and stabilized in pulsed supersonic jets of Ne or Ar. Only the J = 1–0 transition was accessible within the frequency range of the spectrometer. It was measured for the ground (v = 0) and two excited (v = 1, 2) vibrational states. Hyperfine structure due to 183W nuclear spin-rotation coupling was found for 183WO. The overall spectral fit used a Dunham-type expression including Born–Oppenheimer breakdown parameters. Only the v = 0 and 1 states could be fit to the measurement accuracy because of a small perturbation of the v = 2 state. It was necessary to account for the finite nuclear size of the W nucleus in the fit. The resulting parameter V 01W agreed well with a value calculated using density functional theory. Equilibrium internuclear distances re have been evaluated.

First determination of isotopically invariant parameters of the negative ion—Hydrogen sulfide anion (SH −)

The first isotopically invariant Dunham analysis of a negative ion (the hydrogen sulfide anion SH −) that uses all available infrared and sub-millimeter wave experimental data on 32SH −, 33SH −, 34SH −, and 32SD − yields accurate information on Born–Oppenheimer breakdown parameters. The potential constants of expansion of the potential function up to the sixth order were calculated. Differences between the construction of the potential function based on the Morse potential and that on the base of the power series expansion are shown.

The 115Sn, 117Sn and 119Sn nuclear spin-rotation constants in stannous monoxide, SnO, and a new multi-isotopomer analysis

A Fourier transform microwave spectrometer has been used to make high resolution measurements on the J = 1–0 rotational transition for 11 isotopomers of SnO. For the most abundant isotopomer the transition was observed in the v = 0, 1, 2, and 3 states. Magnetic hyperfine structure was observed in the transitions for 115Sn 16O, 117Sn 16O and 119Sn 16O. The nuclear spin-rotation constant C I (Sn) has been determined for these isotopomers for the first time and these constants have been related to nmr shielding parameters. A multi-isotopomer analysis, including data from the 120Sn 17O and 120Sn 18O isotopomers, has been performed on the data. Born–Oppenheimer breakdown parameters were required in the fit and these parameters have been compared to those for the other Sn-chalcogenides.

New observation of the [formula omitted], 1 3Δ g, and 2 3Π g states and molecular constants with all 6Li 2, 7Li 2, and 6Li 7Li data

This paper reports our new observation of the 3 3 Σ g + ( v = 3 – 7 ) , 1 3Δ g ( v = 2–4), and 2 3Π g ( v = 2–8) states of 6Li 7Li by continuous wave perturbation facilitated optical–optical double resonance spectroscopy. Combining our new experimental term values of 6Li 7Li with the available experimental data of 6Li 2 and 7Li 2, molecular constants and potential energy curves by Rydberg–Klein–Rees and direct-potential-fit techniques have been determined. Born-Oppenheimer breakdown parameters of the Li 2 1 3Δ g and 2 3Π g states are calculated.

Isotopically invariant analysis of vibration–rotation transitions of HBr and its isotopologues

The vibration–rotation transition frequencies of HBr and its isotopologues reported in the literature were simultaneously analyzed in a least-squares fit to determine isotopically invariant molecular parameters U kl and Born–Oppenheimer breakdown parameters Δ kl . A total of 692 lines was fitted to Watson’s expression involving 25 adjustable parameters to a weighted unitless standard deviation of σ ≈ 0.91. From new data in the far-infrared region and those of improved precision in the mid-infrared and the near-infrared region, the breakdown parameters for the bromine atom were determined; the parameter Δ 10 Br for the harmonic frequency improved the fit and Δ 01 Br for the rotational constant enabled us to obtain the information on the adiabatic correction to the Born–Oppenheimer approximation.

Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl

Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF 6 or Cl 2, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X 10 + ground states. The spectra have been interpreted with the formalism of 1Σ + molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules.

Infrared and near infrared emission spectra of SbH and SbD

The X 3Σ − ground state vibration–rotation spectrum of SbH and the near infrared spectra of the b 1Σ +– X 3Σ − transitions of SbH and SbD have been measured at high resolution by Fourier transform spectroscopy. The SbH and SbD radicals were generated in a tube furnace with a D.C. discharge of a flowing mixture of argon, hydrogen (or deuterium), and antimony vapor. In the infrared region, the 1–0 and 2–1 bands of the three components (0 +, 1 e , and 1 f ) as well as the 0 + component of the 3–2 band were observed for 121SbH and 123SbH. In the near infrared region, the 0–0, 1–1, and 2–2 bands of the b 1Σ +– X 3Σ − system of both SbH and SbD as well as the 3–3 band of SbD were observed. Except for a few lines, the antimony isotopic shift was not resolved for these electronic spectra. The present data set was combined with the available ground state data on SbD and a 1Δ data for SbH and SbD from previous work, and a least-squares fit was performed for each of the four isotopologues: 121SbH, 123SbH, 121SbD, and 123SbD. Improved spectroscopic constants were obtained for the observed vibrational levels of the X 3Σ −, a 1Δ, and b 1Σ + states of these four isotopologues. In addition, all the above data were also fitted simultaneously to a multi-isotopologue Dunham model, which yielded Dunham constants and Born–Oppenheimer breakdown parameters for these three electronic states. Interestingly, we found that Born–Oppenheimer breakdown corrections were also required for some of the spin–spin and spin–rotation parameters of the X 3Σ − state.

Internuclear distance and effects of Born-Oppenheimer breakdown for PtS, determined from its pure rotational spectrum.

Platinum monosulfide PtS has been prepared in its X0(+) ground electronic state by laser ablation of Pt in the presence of H(2)S. The rotational spectra of eight isotopic species have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. Spectral analysis using a multi-isotopomer Dunham-type expression produced values for Y(01), Y(02), Y(11), and Y(21), along with large values for Born-Oppenheimer breakdown (BOB) parameters for both atoms of the molecule. The BOB parameters are rationalized in terms of the molecular electronic structure and nuclear field shift effects. A large negative (195)Pt nuclear spin-rotation constant has been rationalized in terms of the electron-nucleus dipole-dipole hyperfine constant. The equilibrium bond length in the Born-Oppenheimer approximation has been evaluated.

Vibration-rotation emission spectra and combined isotopomer analyses for the coinage metal hydrides: CuH & CuD, AgH & AgD, and AuH & AuD

High resolution infrared emission spectra have been measured for AuH and AuD and for two isotopomers of each of CuH, CuD, AgH, and AgD. The molecules were made in a carbon tube furnace (King furnace), and in spite of intense background thermal emission from the furnace (at >2000 °C), vibration–rotation emission data could be recorded. Together with high resolution measurements taken from the literature, the data for each species were treated using two types of combined-isotopomer analysis: One based on fits to empirical molecular parameters, and the other based on direct fits to the underlying potential energy functions, both of which take account of mass-dependent Born–Oppenheimer breakdown correction terms. Accurate isotopically related Dunham parameters and Born–Oppenheimer breakdown parameters are obtained for each species, as well as accurate analytic potential functions and adiabatic and nonadiabatic radial correction functions.

The Pure Rotational Spectra of84KrH+and86KrH+1

Rotational absorption spectra of the krypton hydride ion in its ground electronic and vibrational state have been measured with tunable far-infrared radiation. These accurate frequency measurements determine the rotational constantsB,D, andH, and yield transition frequencies accurate to 40 kHz (1σ). By combining the new results with the former microwave data on several isotopic forms ofxKrD+a Dunham analysis can be performed, yielding accurate information on the Born–Oppenheimer breakdown parameters.

The emission spectrum of helium hydride. I. Bands near 8000 Å

Spectra of helium hydride were observed after neutralization of a mass-selected HeH+ beam. The molecules were produced in a fast beam, and so a special setup had to be used to avoid Doppler broadening and a careful calibration procedure had to be applied to determine the line positions and linewidths. In an earlier paper, we reported the first observation of a discrete spectrum of helium hydride, which was discovered by means of an emission band near 8000 Å. In this paper, a detailed analysis of this band for all four stable isotopic mixtures is given. For the deuterides several vibrational bands were observed, which allowed equilibrium molecular constants to be determined. These constants agree with the results of recent ab initio calculations. The similarity of these constants to those of HeH+ in the ground state confirms that the observed states are Rydberg states. Comparison of the molecular constants for different isotopic mixtures shows deviations from the Born–Oppenheimer approximation. Born–Oppenheimer breakdown parameters were derived. Both the upper and lower states show predissociation to the repulsive ground state of helium hydride. The line intensities give evidence of a dependence of the electronic transition moment on the interatomic distance.

Fourier transform emission spectroscopy of NeH+

Abstract The Fourier transform emission spectrum of NeH + was observed. The (1, 0), (2, 1), and (3, 2) vibration-rotation bands of 20 NeH + ; the (1, 0) and (2, 1) bands of 20 NeD + ; and the (1, 0) band of 22 NeH + were recorded from a copper hollow-cathode discharge in neon and hydrogen. Molecular constants, including Born-Oppenheimer breakdown parameters, were extracted from the data.