A photoelectron spectroscopic study of the second ionisation of the CF(X2Π) radical

The CF(X²Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF⁺(X¹Σ⁺)←CF(X²Π) and CF⁺(a³Π)← CF(X²Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ω_e and r_e to be determined as 1810±30 cm⁻¹ and 1.154±0.005 Å, respectively for the first ionic state, CF⁺(X¹Σ⁺), and 1614±30 cm⁻¹ and 1.213±0.005 Å, respectively for the second ionic state, CF⁺(a³Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.     

A Realization of the W_(1+∞) Algebra and Its n-Algebra

We consider a realization of the W_(1+∞) algebra and investigate its n-algebra, which is different from the n-algebra of Zhang et al. [2016 arXiv:1606.07570 v2] It is found that the generators W_m~s with any fixed superindex s ≥ 1 yield the null sub-2 s-algebra. The nontrivial sub-4-algebra and Virasoro-Witt 3-algebra are presented. Moreover,we extend the generators to the multi-variables case. These generators also yield the W_(1+∞) algebra and null n-algebras.     

A new study of the ν 2(A 1) infrared band of phosphorus trifluoride

The high-resolution Fourier transform infrared spectrum of phosphorus trifluoride (PF₃) has been reinvestigated in the v_2?=?1 vibrational excited state near 487?cm^?1 (at a resolution of 3?×?10^–3?cm^–1). Thanks to our new accurate rotational ground-state C ₀ value, 0.159970436(69)?cm^–1, and to recent pure rotational measurements, 318 new infrared transitions of the ν ₂ fundamental band have been assigned, extending the rotational quantum number values up to K _max?=?71 and J _max?=?72. A merge, for the first time, of 135 reported microwave data (K _max?=?42 and J _max?=?49) within the v_2?=?1 excited level and 2860 rovibrational transitions yielded improved constants of ν ₂. Parameters of this band have been obtained, up to sextic centrifugal distortion constants, by least-squares fits, σ _IR?=?3.60?×?10^–4?cm^–1 and σ _MW?=?5.53?×?10^–6?cm^–1 (166?kHz). Comparison of these constants with those measured previously by infrared spectroscopy reveals orders of magnitude higher accuracy of these new values.     

Status and Plan of the HL-2A Project

HL-2A is a new divertor tokamak under construction at Southwestern Institute of Physics (SWIP), Chengdu, China, based on the experience from HL-1 and HL-1M. HL is the short term of a Chinese word that means “ Toroidal Current Device“ . The main objectives of HL-2A are to produce more adaptable divertor configurations to study energy exhaust and impurity control(the first divertor tokamak plasma in China), and to study enhanced plasma confinement by profile control and moderate plasma shaping.     

Influence of ro-vibrational and isotope effects on the dynamics of the C(3 P)+ OD(X 2Π) → CO(X 1 Σ+) + D(2 S) reaction

The C(³ P)+OD(X ²Π) reaction has been studied by means of quantum mechanical real wave packet (RWP) and quasiclassical trajectory (QCT) methodologies on the ground potential energy surface of Zanchet et al. [J. Phys. Chem. A 110, 12017 (2006)]. Initial state selected total reaction probabilities at J?=?0 total angular momentum have been calculated for a wide range of collision energies. Product state-resolved integral cross-sections at selected collision energies and excitation functions have been determined from the RWP calculations using the J-shifting approximation and from QCT calculations. State-specific and thermal rate coefficients have been calculated using both methodologies up to 500 K. The effect of reagent rotational excitation on the dynamics for the C(³ P)+OH(X ²Π) and C(³ P)+OD(X ²Π) reactions has been investigated and interesting discrepancies between the QCT and RWP results have been found. The RWP results are found to be in an overall good agreement with the corresponding QCT results, although the QCT integral cross-section and rate coefficients are slightly smaller than those obtained from the RWP calculations.     

The ion-molecule reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the predissociation of the A2Σ+ and B2Π states of N2O+

The potential energy surfaces (PESs) for several electronic states involved in the reaction O⁺ (⁴S) + N₂(X¹Σ⁺) → NO⁺ (X¹Σ ⁺, v′) + N(⁴S) and the role of the ionic N₂O⁺ intermediate have been investigated by ab initio calculations. The ⁴A″ PES, which correlates with the ground state educts, has a barrier of about 1 eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X² Π electronic ground state of the N₂O⁺ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1 eV, the reaction proceeds mainly on the adiabatic PES of the ⁴A″ state. The A²Σ⁺ state of N₂O⁺ predissociates via a vibronic coupling with the B²Π state, and in bent structures via a spin-orbit coupling with the ⁴A″ component of the ⁴II state. The electronic structure of the B²Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N₂O⁺.     

A comprehensive model for the quantification of linear and nonlinear regime laser-induced fluorescence of OH under A2Σ+←X2Π(1,0) excitation

An analytic model termed the ‘integrated quasi-steady-state’ (IQSS) model for the comprehensive quantification of both linear and nonlinear regime laser-induced fluorescence (LIF) is presented. The IQSS model is optimized for the hydroxyl radical (OH), subject to nanosecond A²Σ⁺←X²Π(1,0) excitation at pressures close to atmospheric. The IQSS model is particularly relevant to experimental conditions where the LIF signal is both spectrally and temporally integrated, such as in planar laser-induced fluorescence experiments. The IQSS model is based around a quasi-steady-state solution to a four-level rate-equation approximation of the OH molecule; this quasi-steady-state solution is then integrated with a triangular functional form for both the spatial and temporal variations to produce an analytic solution. In order to accurately predict LIF in the nonlinear regime, it is shown that both the temporal and the spatial variations of the laser pulse—or ‘wings’ of the laser pulse—must be adequately accounted for in the LIF model formulation. The IQSS model is successfully verified against detailed numerical simulations for variations in the laser irradiance, quenching environment and temperature. Experimentally, the IQSS model is successfully validated by comparing the predicted and measured OH LIF vs. irradiance dependence in the product gases of a methane–air laminar flame.     

Exact quantum dynamics study of the H(2S)+SiH+(X1Σ+) reaction on a new potential energy surface of SiH2+(X2A1)

Based on a new global potential energy surface of SiH₂⁺(X²A₁), the exact quantum dynamical calculation for the H(²S)+SiH⁺(X¹Σ⁺)→H₂+Si⁺ reaction has been carried out by using the Chebyshev wave packet method. The initial state specified (ν_i=0, j_i=0) probabilities, integral cross sections (ICS) and thermal rate constants of the title reaction are calculated. All partial wave contributions up to J=90 are calculated in exact quantum calculation including the full Coriolis coupling (CC) effect. The dynamical behaviors of probabilities, ICSs and rate constants are found to be in accord with an exothermic reaction without potential barrier. By comparing the probabilities of CC with the corresponding centrifugal sudden (CS) approximation ones, it can be concluded that neglecting CC effect will decrease the collision time, increase the amplitude of oscillation and lead to overestimation or underestimation of the reaction probability. For ICSs and rate constants, it is found that the deviation of CC and CS ICSs is small in the most of collision energy range except for the range of 0 eV-0.05 eV, while the deviation of both rate constants is considerable in the temperature range of 16 K-1000 K.     

Submillimeter-wave spectroscopy of VN (XΔr) and VO (XΣ): A study of the hyperfine interactions

The pure rotational spectra of VN (X³Δ_r) and VO (X⁴Σ⁻) have been recorded in the frequency range 290-520 GHz using direct absorption spectroscopy. These radicals were synthesized in the gas-phase from the reaction of VCl₄ with either N₂ or H₂O in an AC discharge. Seven rotational transitions were recorded for each molecule; in both sets of spectra, fine and hyperfine structures were resolved. The data sets for VN and VO were fit with Hund’s case (a) and case (b) Hamiltonians, respectively, and rotational, fine structure, and hyperfine constants determined. For VN, however, an additional hyperfine parameter, Δa, was necessary for the analysis of the Ω = 2 sublevel to account for perturbations from a nearby ¹Δ state, in addition to the usual Frosch and Foley constants. Determination of Δa suggests that the ¹Δ state lies ∼3000 cm⁻¹ above the ground state. In VO, the hyperfine structure in the F₂ and F₃ components was found to become heavily mixed due to an avoided crossing, predicted by previous optical studies to be near the N = 15 level. The hyperfine constants established for these two molecules are consistent with the proposed σ¹δ¹ and σ¹δ² electron configurations.     

A semimetal model of the normal state magnetic susceptibility and transport properties of Ba(Fe1−xCox)2As2

A simple two-band 3D model of a semimetal is constructed to determine which normal state features of the Ba(Fe_1?xCo_x)₂As₂ superconductors can be qualitatively understood within this framework. The model is able to account in a semiquantitative fashion for the measured magnetic susceptibility, Hall, and Seebeck data, and the low temperature Sommerfeld coefficient for 0 < x < 0.3 with only three parameters for all x. The purpose of the model is not to fit the data but to provide a simple starting point for thinking about the physics of these interesting materials. Although many of the static magnetic properties, such as the increase of the magnetic susceptibility with temperature, are reproduced by the model, none of the spin-fluctuation dynamics are addressed. A general conclusion from the model is that the magnetic susceptibility of most semimetals should increase with temperatures.     

π-Electron Densities in Molecules ΦCHX1X2 and Correlation with the Intensity of the 00 Band of the Secondary Transition

In molecules such as ΦX₁X₂X₃the intensity of the secondary transition of the benzene chromophore, strongly depends on long range interactions involving a σ·π coupling between orbitals belonging to the C_α-X bonds, and the πΦ system. Such a coupling distorts the symmetry of the π_Φ system(1–5). The secondary transition (towards 260 nm) which is forbidden when the symmetry is D_6h - as in the benzene molecule itself where only the low intensity progression A isobserved - becomes all the more allowed as the substituent is able to distort the πΦ cloud towards a C_2V symmetry. A new progression called B is observed. Its intensity is usually evaluated by the measure of its 00 band. The distorsion of symmetry arises because of the π donating or π withdrawing electronic effects of the substituent(1–7). These phenomena have been explained on the ground of a V shaped function(l) : ε₀₀ = f(σ), where σ is a parameter linked to the electronic effects of the substituents. When the whole substituent is a π donating one, its π donating effect is lowered by an increase of the electron attracting power of the groups X : the perturbation of the D_6h symmetry is lessened and ε₀₀ decreases. On the contrary, when the whole substituent is a π withdrawing one, an increase of the withdrawing power of the groups X increases the withdrawing power of the whole substituent, the distorsion of the D6h symmetry increases and ε₀₀ increases too. The minimum of the V shaped curve correspond to the species for which the π donating tendency of the aliphatic part of the substituent is quenched by the electron withdrawing tendency of the groups X. The D_6h symmetry of the πΦ cloud is restored. The transition is forbidden and the system A only is observed.     

Analysis of the High-Resolution Infrared Spectrum of the PHD2 Molecule: ν1 and 2ν1 Bands

The results of investigation into the infrared spectra of the PHD₂ molecule including the ₁ fundamental band centered at 2324.005 cm^–1 (with a resolution of 4.2·10^–3 cm^–1) and the first 2₁ valence overtone centered at 4563.634 cm^–1 (with a resolution of 8.8·10^–3 cm^–1) are given in the present paper. Based on an analysis of the results obtained, 1340 and 1020 lines are referred to the ₁ and 2₁ bands, respectively. This data are used to calculate 316 and 248 vibrational-rotational energies of the (100000) and (200000) excited vibrational states, respectively. Since both bands can be considered as isolated, we take advantage of the Watson Hamiltonian (the reduction A in the I ^r representation) to describe their rotational structure. The calculated spectroscopic parameters of the examined states of the PHD₂ molecule correlate well with each other and with the corresponding parameters of the ground vibrational state.     

High-resolution laser spectroscopy of CaNH2: Analysis of the C̃2A1-X̃2A1 system

Laser excitation spectra of the $\text{C}\text{?}{}^2\text{A}{}_1\text{-}\text{X}\text{?}{}^2\text{A}{}_1$ system of CaNH₂ are reported. Due to the spectral density, individual lines could only be resolved and measured using a filtered fluorescence excitation technique, with a monochromator acting as an optical bandpass filter; 140 line positions were measured in this way and assigned to the parallel K_?1 = 1 subband of what is believed to be the vibrational 0-0 band. The molecular constants were determined from a weighted nonlinear least-squares fit of the line positions.

     

19.

Einstein A coefficients and absolute line intensities for the E2Π–X2Σ+ transition of CaH     

Gang Li  Jeremy J. Harrison  Ram S. Ram  Colin M. Western  Peter F. Bernath 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(1):67-74

Einstein A coefficients and absolute line intensities have been calculated for the E²Π–X²Σ⁺ transition of CaH. Using wavefunctions derived from the Rydberg–Klein–Rees (RKR) method and electronic transition dipole moment functions obtained from high-level ab initio calculations, rotationless transition dipole moment matrix elements have been calculated for all 10 bands involving v′=0,1 of the E²Π state and v″=0,1,2,3,4 of the X²Σ state. The rotational line strength factors (Hönl–London factors) are derived for the intermediate coupling case between Hund's case (a) and (b) for the E²Π–X²Σ⁺ transition. The computed transition dipole moments and the spectroscopic constants from a recent study [Ram et al., Journal of Molecular Spectroscopy 2011;266:86–91] have been combined to generate line lists containing Einstein A coefficients and absolute line intensities for 10 bands of the E²Π–X²Σ⁺ transition of CaH for J-values up to 50.5. The absolute line intensities have been used to determine a rotational temperature of 778±3 °C for the CaH sample in the recent study.     

20.

Potential of the A 1Σ u + state of He2     

Shaul Mukamel  Uzi Kaldor 《Molecular physics》2013,111(6):1107-1117

The potential of the lowest excited singlet state of He₂ is calculated. The best function includes 209 configurations constructed from 10 σ basis orbitals. Excellent agreement with experimental quantities depending on the shape of the potential near the minimum (equilibrium interatomic separation, vibrational and rotational constants for the lower vibration levels) is obtained. The dissociation energy is 18 600 cm^-1, compared to the experimental 19 910±50 cm^-1. Agreement is not as good for the highest vibrational levels.     

		Main parameters
	$\text{X}\text{?}{}^2\text{A}{}_1$	$\text{C}\text{?}{}^2\text{A}{}_1$
$\text{T}{}_{\mathrm{k?1}}\text{= 1}$	3-	17375.129(5)
B	0.30079(6)	0.30562(6)
C	0.29319(6)	0.29789(8)
$\text{?}{}_{\mathrm{aa}}$	3-	?0.66(4)
$\text{?}{}_{\mathrm{bb}}$	3-	?0.0356(8)
$\text{?}{}_{\mathrm{cc}}$	3-	?0.0453(8)

Einstein A coefficients and absolute line intensities for the E2Π–X2Σ+ transition of CaH

Einstein A coefficients and absolute line intensities have been calculated for the E²Π–X²Σ⁺ transition of CaH. Using wavefunctions derived from the Rydberg–Klein–Rees (RKR) method and electronic transition dipole moment functions obtained from high-level ab initio calculations, rotationless transition dipole moment matrix elements have been calculated for all 10 bands involving v′=0,1 of the E²Π state and v″=0,1,2,3,4 of the X²Σ state. The rotational line strength factors (Hönl–London factors) are derived for the intermediate coupling case between Hund's case (a) and (b) for the E²Π–X²Σ⁺ transition. The computed transition dipole moments and the spectroscopic constants from a recent study [Ram et al., Journal of Molecular Spectroscopy 2011;266:86–91] have been combined to generate line lists containing Einstein A coefficients and absolute line intensities for 10 bands of the E²Π–X²Σ⁺ transition of CaH for J-values up to 50.5. The absolute line intensities have been used to determine a rotational temperature of 778±3 °C for the CaH sample in the recent study.     

Potential of the A 1Σ u + state of He2

The potential of the lowest excited singlet state of He₂ is calculated. The best function includes 209 configurations constructed from 10 σ basis orbitals. Excellent agreement with experimental quantities depending on the shape of the potential near the minimum (equilibrium interatomic separation, vibrational and rotational constants for the lower vibration levels) is obtained. The dissociation energy is 18 600 cm^-1, compared to the experimental 19 910±50 cm^-1. Agreement is not as good for the highest vibrational levels.