Line lists for the b1Σ+-X3Σ− and a1Δ-X3Σ− transitions of SO

Line strengths have been calculated in the form of Einstein A coefficients and f-values for a large number of bands of the A 2Π-X 2Σ+ and B 2Σ+-X 2Σ+ systems and rovibrational transitions within the X 2Σ+ state of CN using Western's PGOPHER program. The J dependence of the transition dipole moment matrix elements (the Herman-Wallis effect) has been taken into account. Rydberg-Klein-Rees potential energy functions for the A 2Π, B 2Σ+ , and X 2Σ+ states were computed using spectroscopic constants from the A 2Π-X 2Σ+ and B 2Σ+-X 2Σ+ transitions. New electronic transition dipole moment functions for these systems and a dipole moment function for the X 2Σ+ state were generated from high level ab initio calculations and have been used in Le Roy's LEVEL program to produce transition dipole moment matrix elements (including their J dependence) for a large number of vibrational bands. The program PGOPHER was used to calculate Einstein A coefficients, and a line list was generated containing the observed and calculated wavenumbers, Einstein A coefficients and f-values for 290 bands of the A 2Π-X 2Σ + transition with v′ = 0-22, v″ = 0-15, 250 bands of the B 2Σ+-X 2Σ+ transition with v′ = 0-15, v″ = 0-15 and 120 bands of the rovibrational transitions within the X 2Σ+ state with v = 0-15. The Einstein A coefficients have been used to compute radiative lifetimes of several vibrational levels of the A 2Π and B 2Σ + states and the values compared with those available from previous experimental and theoretical studies. © 2014. The American Astronomical Society.

Mars has changed from a warmer, water-containing planet into a cold and arid environment. Collisions of superthermal oxygen and other atoms with surrounding gases may lead to the escape of light atmospheric molecules, such as D1, OH2, He3, and H24, from the Martian atmosphere. Such processes have probably contributed to the thinning of its atmosphere and the transformation of Mars' climate. OH molecules can be produced in the Martian atmosphere by the photodissociation of water vapor and in several chemical reactions, such as the reactions of thermal molecular hydrogen and energetic oxygen atoms O + H2 → H + OH 5. Emission and absorption spectra of OH molecules within the Martian atmosphere can lead to a better understanding of these processes. For example, they can help monitor the variation of its abundance with altitude 6. In general, astronomical spectra of specific molecules can be better interpreted through a detailed identification of their line list. In this work, we present an extensive line list for the B2S+ - X2P and D2S- - X2P electronic transitions of OH, including line intensities, line positions with the relevant quantum numbers of the upper and lower states, e/f parity and oscillator strength, calculated using PGOPHER7 program. The line intensities are found based on calculated ab-initio Transition Dipole Moment Function and potential energy curves obtained using the quantum computational chemistry program MOLPRO8, using CASSCF method followed by MRCI including Davidson correction term (+Q). LEVEL9 program is used to compute Transition Dipole Moment Matrix Elements in Hund's case (b) using the procedure of Numerov-Cooley10 which are then transformed to Hund's case (a) as required by PGOPHER.   1 P. Zhang, V. Kharchenko, M. Jamieson, and A. Dalgarno, "Energy Relaxation in Collisions of Hydrogen and Deuterium with Oxygen Atoms," J.  Geophys. Res. 114, A07101 (2009).   2 M. Gacesa, N. Lewkow, and V. Kharchenko, "Non-thermal escape of molecular hydrogen from Mars," Icarus, L10203 (2012). 3 S. Bovino et al., "Energy Transfer in O Collisions with He Isotopes and Helium Escape from Mars," Geophys. Res. Lett., 38, L02203 (2011). 4 M. Gacesa, P. Zhang, and V. Kharchenko, "Non-thermal escape of molecular hydrogen from Mars," Geophys. Res. Lett., 39, L10203 (2012). 5 M. Gacesa, N. Lewkow and V. Kharchenko, "Non-thermal production and escape of OH from the upper atmosphere of Mars". Icarus, 284, pp.90-96 (2017). 6 S. Raghuram, A. Bhardwaj, & M. Dharwan, “Model for Nitric oxide and its dayglow emission in the Martian upper atmosphere using NGIMS/MAVEN measured neutral and ion densities”. Icarus, 382, 115010 (2022). 7 CM. Western, PGOPHER: a program for simulating rotational, vibrational and electronic spectra. J Quant Spectrosc Radiat Transf., 186:221–42 (2017). 8 HJ. Werner, PJ. Knowles, G. Knizia, FR. Manby, M. Schütz, Molpro: a general purpose quantum chemistry program package. J Chem Phys., 2:242–53 (2011). 9 RJ. LeRoy, "LEVEL: A computer program for solving the radial Schrödinger equation for bound and quasibound levels." J Quant Spectrosc Radiat Transf., 186:167–78 (2017). 10 J. W. Cooley, "An improved eigenvalue corrector formula for solving the Schrödinger equation for central fields," Math. Comput., vol. 15, no. 76, pp. 363–374, (1961).  

The emission and absorption spectra of the A1Π - X1Σ+ transition of the MgH− anion are generated at various temperatures. These spectra are investigated from the calculation of the line positions and line intensities, which are fundamental for spectroscopic modeling. The line positions are determined using molecular constants from literature for the A1Π - X1Σ+ states of the MgH−. To obtain accurate line intensities, highly accurate ab-initio Transition Dipole Moment Functions (TDMFs) and potential energy curves (PECs) from the literature were employed. The Transition Dipole Moment Matrix Elements (TDMMEs) are computed in Hund’s case (b) coupling using LeRoy’s LEVEL program. These matrix elements were then transformed from Hund’s case (b) to Hund’s case (a) to incorporate electron spin, which are then used in PGOPHER to generate the line lists. Additionally, Einstein A coefficients and oscillator strengths are provided in this work for the first time.

Potential energy, electric dipole, and electronic transition moment functions have been calculated for several bound electronic states of CH− and NH− from accurate electronic wave functions. Spectroscopic constants for the X 2Π state of NH− have been compared with the data recently obtained by laser induced autodetachment spectroscopy. Spectroscopic constants of the A 2Σ+ state of NH− and radiative X 2Π–A 2Σ+ transition probabilities are presented. Spectroscopic constants and infrared transition probabilities for the X 3Σ− and the a 1Δ states of CH− have been calculated. The radiative lifetime of v=1 in CH−(X 3Σ−) is found to be in a very good agreement with a recent experimental value. The transition probabilities are for both ions much larger than those of their neutral counterparts, and increase in the series OH−, NH−, CH−.

The Autler–Townes Effect in Molecules: Observations, Theory, and Applications

The magneto-optical Faraday effect is determined by the electric dipole and magnetic dipole transitions in a transparent magnetic material. At the same time, the inverse Faraday effect is still described by an expression that includes only electric dipole transitions. The magnetic dipole contribution to the inverse Faraday effect is considered theoretically, and the dependence of the inverse Faraday effect on the wavelength in the near-infrared range (where the magnetic dipole contribution becomes significant) is obtained by the example of a ferrite–garnet film. It is shown that, although both contributions to the inverse Faraday effect always take place for homogeneous films, only the magnetic-dipole inverse Faraday effect manifests itself for films with a periodic nanostructure upon excitation by a TE waveguide mode, which may be useful for its experimental observation.

A spherical tensor expansion is carried out to express the resonant inelastic scattering cross-section as a sum of products of fundamental spectra with tensors involving wavevectors and polarization vectors of incident and scattered photons. The expression presented in this paper differs from that of the influential article by Carra et al. (Phys. Rev. Lett. 74, 3700, 1995) because it does not omit interference terms between electric dipole and quadrupole contributions when coupling each photon to itself. Some specific cases of the spherical tensor expansion are discussed. For example the case of isotropic samples is considered and the cross-section is expressed as a combination of only three fundamental spectra for the situation where electric dipole or electric quadrupole transitions in the absorption process are followed by electric dipole transitions in the emission. This situation includes the case of untextured powder samples, which corresponds to the most frequent situation met experimentally. Finally, it is predicted that some circular dichroism may be observed on isotropic samples provided that the circular polarization of the scattered beam can be detected.

The problem of dipole transition-matrix element calculation for optical transitions in multiply charged one-electron diatomic quasimolecules with unequal nuclear charges ${Z}_{1}$ and ${Z}_{2}$ has been stated and solved. The quasimolecule ${Z}_{1}e{Z}_{2}$ is a unique example of a two-center system for which the energy terms and dipole transition moments have been calculated precisely in the frame of a nonrelativistic approach. Particular examples for the optical transitions with ${Z}_{1}=1.5,2,2.5,3$ and ${Z}_{2}=1$ and with the principal quantum number of the united ion ${n}_{u}=1,2,3,4$ have been tabulated. The scaling rules make it possible to determine the matrix elements for quasimolecules having nuclear charge ratios such as 2:1, 3:1, 3:2, and 5:2. Zeros at intermediate $R$ and zero limiting values at large $R$ are the highlighted features of the matrix elements. The heteronucleus case generates a large number of asymptotically forbidden transitions corresponding to transitions of an electron from one ion to another.

An experimental method is demonstrated that allows determination of the ratio between the electric (E1) and magnetic (M1) transition dipole moments in the A-X band of OH, including their relative sign. Although the transition strengths differ by more than 3 orders of magnitude, the measured M1-to-E1 ratio agrees with the ratio of the abinitio calculated values to within 3%. The relative sign is found to be negative, also in agreement with theory.

The transition electric dipole moments between low-lying valence states of NH{sup +} are calculated by an ab initio effective valence-shell Hamiltonian (H{sup v}) method. The H{sup v} calculated transition moments are found to be in good agreement with those by other accurate ab initio methods. The spontaneous emission probabilities for the A{sup 2}{Sigma}{sup - }{r_arrow} X{sup 2}{product}, B{sup 2}{Delta} {r_arrow} X{sup 2}{product}, C{sup 2}{Sigma}{sup +} {r_arrow} X{sup 2}{product} transitions of NH{sup +} are computed. Also, radiative lifetimes for A{sup 2}{Sigma}{sup -}, B{sup 2}{Delta}, and C{sup 2}{Sigma}{sup +}states are all theoretically determined using the potential energy functions by H{sup v}. Also, the H{sup v} results are well compared with those computed using the Morse potentials and the RKR potentials which are obtained from experimental data. 18 refs., 4 figs., 5 tabs.

This paper is the first part of a series devoted to the ab initio calculation of some vibrational properties helpful in the interpretation of high resolution spectroscopy, atmospherical and astrophysical data. An ab initio method of calculation of the vibrational transition energies and dipole moment matrix elements is described and analyzed. The main features of this method are the resolution of both electronic and vibrational problems by analytical variational techniques and the representation of the potential energy and dipole moment hypersurfaces as Taylor's series expansions in normal coordinates up to the fourth order. The dipole moment matrix elements are then evaluated by simple analytical formulae. In this first paper, some of the approximations inherent to the methodology are systematically analyzed on the basis of results obtained for diatomic molecules (BeH, HF, NH and NO) with a comparison to experimental and other theoretical results found in the literature. The dependence on the results of the effects of electrical and mechanical anharmonicities, electron correlation and basis set dependencies are investigated. The applicability of the method to small polyatomic systems is discussed in the second paper of this series, on the basis of test calculations on the water molecule.

We present a theroretical treatment of electric dipole (E1) transitions of heavy quarkonia based on effective field theories. Within the framework of potential nonrelativistic QCD (pNRQCD) we derive the complete set of relativistic corrections at relative order $v^2$ to the decay rate in a systematic, model-independent way. Former results from potential model calculations will be scrutinized and a phenomenological analysis with lattice input in relation to experimental data will be presented.

The concept of robustness of rotational strengths of vibrational modes in a VCD spectrum has been introduced as an aid in assignment of the absolute configuration with the help of the VCD spectrum. The criteria for robustness have been based on the distribution around 90° of the angles ξ(i) between electric and magnetic transition dipoles of all the modes i of a molecule. The angles ξ(i) (not, of course, the rotational strengths) are, however, dependent on the choice of origin. The derived criteria are for the center of mass chosen as the origin of the coordinate system. We stress in this note that application of the derived criteria assumes that excessive translation of the coordinate origin is not applied. Although the ξ(i) angles are not very sensitive to the position of the origin, very small displacements (a few Å) are not a problem, excessive translation of the origin does have considerable effect on the ξ(i) angles. In this note we quantify this effect and demonstrate how the distribution of ξ(i) angles is affected. Although it is possible to recalibrate the robustness criteria for the angles for a specific (large) displacement, we recommend that such displacement simply be avoided. It is to be noted that some modeling software does yield output with excessively displaced coordinate origin; this should be checked and corrected.

Herein we report a two‐directional cyclization strategy for the synthesis of highly strained depth‐expanded oxygen‐doped chiral molecular belts of the zigzag‐type. From the easily accessible resorcin[4]arenes, an unprecedented cyclization cascade generating fused 2,3‐dihydro‐1H‐phenalenes has been developed to access expanded molecular belts. Stitching up the fjords through intramolecular nucleophilic aromatic substitution and ring‐closing olefin metathesis reactions furnished a highly strained O‐doped C2‐symmetric belt. The enantiomers of the acquired compounds exhibited excellent chiroptical properties. The calculated parallelly aligned electric (μ) and magnetic (m) transition dipole moments are translated to the high dissymmetry factor (|glum| up to 0.022). This study provides not only an appealing and useful strategy for the synthesis of strained molecular belts but also a new paradigm for the fabrication of belt‐derived chiroptical materials with high CPL activities.

A two-way electron paramagnetic resonance cavity for magnetic dipole transition (MDT) and electric dipole transition (EDT) was manufactured. There are two openings to fit the sample cell for MDT and for EDT in the cylindrical TE 011 mode. One opening is located on the axis of the cavity and the other is located away from the axis. EPR spectra obtained from the mixture of oxygen and nitrogen oxide when the sample cell was inserted in each opening showed the selective transition of the MDT or of the EDT of the species. When dc electric field parallel to the steady magnetic field was applied to the nitrogen oxide located away from the axis, each of the EDT peaks was divided into two peaks, one of which was higher than the other. The magnitude of the splitting was proportional to the electric field strength, in agreement with the theory. The permanent electric dipole moment 0.159 × 10 −18 cgs esu obtained agreed with the value reported in the literature.