Valence Correlation Corrections Research Articles

Transition properties of a2Σ–, b2Δ, c2Π, d2Π, and e2Σ+ electronic states of aluminum silicon radical

Detecting aluminum silicon can yield useful information concerning the depletion of silicon and aluminum and their recycling in astrophysical sources. In addition, such detection can be helpful for understanding gas–phase aluminum and silicon chemistry in the interstellar/circumstellar atmosphere. However, only a few transition properties of this radical have been reported. Therefore, the potential energy curves of several lowest–lying doublet states and the transition dipole moments between them were calculated using the icMRCI approach. Core–valence correlation correction, scalar relativistic correction, and spin–orbit coupling effect were included to improve the accuracy of transition properties. The radiative lifetimes of the first 16 levels were approximately 4.8 – 679.5 ms for the c2Π1/2 state, 2.2 – 431 ms for the c2Π3/2 state, 29.3 – 40.4 µs for the d2Π1/2 state, 21.2 – 30.1 µs for the d2Π3/2 state, and 88.7 – 175.6 µs for the e2Σ+1/2 state. The spontaneous emissions from the c2Π1/2 and c2Π3/2 states to the a2Σ–1/2, b2Δ3/2, and b2Δ5/2 states and those from the e2Σ+1/2 state to the d2Π1/2 and d2Π3/2 states were located in the radio–frequency region. The d2Π1/2 – a2Σ–1/2 and d2Π3/2 – a2Σ–1/2 transitions were the strongest, followed by d2Π1/2 – b2Δ3/2, d2Π3/2 – b2Δ3/2, d2Π3/2 – b2Δ5/2, d2Π1/2 – c2Π1/2, d2Π3/2 – c2Π3/2, e2Σ+1/2 – c2Π1/2, and e2Σ+1/2 – c2Π3/2 transitions. The spontaneous emissions from these systems were located in the infrared region. The variation in the radiative lifetime of a level υ versus the rotational quantum number J was investigated for the d2Π1/2, d2Π3/2, and e2Σ+1/2 states.

Rovibrational properties of the A1Π – X1Σ+ system of the AlCl radical

The potential energy curves of the X1Σ+ and A1Π states of aluminum monochloride radical and the transition dipole moments between them were calculated using the icMRCI approach. Core–valence correlation and scalar relativistic corrections were applied. The extrapolation of the potential energies to the complete basis set limit was considered to improve the quality of the potential energy curves. In order to accurately calculate the rovibrational transition positions of the A1Π – X1Σ+ system, the experimental Te value of the A1Π state was used to improve the reliability of the ab initio results. The radiative lifetimes of all vibrational states of the A1Π state were calculated and compared with the available experimental and theoretical results. The variation of the radiative–lifetime distribution with the rotational quantum number was obtained. The rovibrational transition positions, Einstein A coefficients, oscillator strengths, and Franck–Condon factors of the P, Q, and R branches of the vibronic emissions of this system were calculated up to J = 150. The Einstein A coefficients were large for numerous vibronic bands, indicating that these transitions were easily measured via spectroscopy. A Comparison with available measurements shows that the transition properties reported herein are accurate.

Investigations on transition properties of X2Σ+, A2Π, B2Σ+, C2Π, and a4Σ+ states, and their Ω states of BO

The transition properties were calculated for the X2Σ+, A2Π, B2Σ+, C2Π, and a4Σ+ states, and eight Ω states of BO. The calculations were performed using the CASSCF method, followed by the icMRCI approach. Core–valence correlation and relativistic corrections were included. The radiative lifetimes of the first 16 vibrational levels were roughly 1.5–1.6 μs for the A2Π state, 96–177 ns for the B2Σ+ state, and 16.7–18.5 ns for the C2Π state. The B2Σ+ – X2Σ+ and C2Π – X2Σ+ transitions were strong, followed by the A2Π – X2Σ+, B2Σ+ – A2Π, and C2Π – A2Π transitions. The radiative lifetime of the first 16 levels was approximately 4.9–10.4 ms for the a4Σ+1/2 state, 0.21–24 ms for the a4Σ+3/2 state, 2.9–3.6 μs for the A2Π1/2 state, 3.5–3.8 μs for the A2Π3/2 state, 134–230 ns for the B2Σ+1/2 state, 23.2–25.4 ns for the C2Π1/2 state, and 23.0–25.2 ns for the C2Π3/2 state. Among all spin–forbidden transitions generated from the a4Σ+ state, the a4Σ+1/2 – X2Σ+1/2 and a4Σ+3/2 – X2Σ+1/2 transitions were relatively strong. The transition properties reported herein were compared with the experimental results. The variation of the radiative–lifetime distribution with the rotational angular quantum number was evaluated for A2Π1/2, A2Π3/2, B2Σ+1/2, C2Π1/2, and C2Π3/2 states. It is expected that the transition properties calculated in this study can provide some useful guidelines for future experimental and theoretical investigations.

Radiative lifetimes of A 2Π, B 2Σ+, a 4Σ+, and b 4Δ states of CP radical

The potential energy curves of X 2Σ+, A 2Π, B 2Σ+, a 4Σ+, and b 4Δ states and their Ω states of CP were calculated using the icMRCI approach. The transition dipole moments between these states were computed. To improve the accuracy of the potential energy curves, core–valence correlation and scalar relativistic corrections were considered. The radiative lifetimes were approximately 10 μs for the A 2Π3/2 and A 2Π1/2 states and 100 ns for the B2Σ+1/2 state; those were approximately 10, 10 – 100, 10, 0.1 – 1, and 10 ms for the a 4Σ+1/2, a 4Σ+3/2, b 4Δ1/2, b 4Δ3/2, and b 4Δ5/2 states, respectively. The spontaneous emissions from the B 2Σ+1/2 – X 2Σ+1/2 system were strong, followed by the A 2Π3/2 – X 2Σ+1/2, A 2Π1/2 – X 2Σ+1/2, B 2Σ+1/2 – A 2Π3/2, and B 2Σ+1/2 – A 2Π1/2 transitions. The strong emissions from the A 2Π3/2 – X 2Σ+1/2 and A 2Π1/2 – X 2Σ+1/2 systems were in the infrared region; those from the B 2Σ+1/2 – X 2Σ+1/2 system were in the visible and ultraviolet regions; and those from the B 2Σ+1/2 – A 2Π3/2, and B 2Σ+1/2 – A 2Π1/2 systems were of visible light. A simple comparison shows that the effect of the spin–orbit coupling on the radiative lifetimes of the A 2Π and B 2Σ+ states was significant. The radiative–lifetime distribution of each level υ versus the rotational quantum number J was evaluated for υ ≤ 15 and J ≤ 70.5.

Transition properties of X1Σ+, A1Σ−, B1Δ, C1Π, a3Σ+, b3Δ, c3Π, and d3Σ− states of PO+

The potential energy curves of the X1Σ+, A1Σ–, B1Δ, C1Π, a3Σ+, b3Δ, c3Π, and d3Σ– states of PO+ and the transition dipole moments between these states were calculated using the CASSCF method, and then the icMRCI approach. To accurately compute the transition properties, core–valence correlation and scalar relativistic corrections were taken into account. The spin–orbit coupling calculations were used to determine the transition properties of the A1Σ–, B1Δ, a3Σ+, and b3Δ states, from which no spontaneous emissions were generated owing to the limitations from the dipole–allowed transition selection rule. The radiative lifetime was approximately 10 – 100 ns for the C1Π state and 10 μs for the c3Π state. Among these dipole–allowed transitions, the emissions from the C1Π – X1Σ+ system was the strongest and was followed by the C1Π – A1Σ– and c3Π – a3Σ+ transitions. The radiative lifetime was approximately 10 – 100, 10 – 100, and 100 μs for the A1Σ–0–, d3Σ–0+, and d3Σ–1 states, respectively. Those were of the order of 0.1 – 10, 10, 10 – 100, 1 – 100, and 0.1 – 1 ms for the B1Δ2, a3Σ+1, a3Σ+0–, b3Δ1, and b3Δ2 states, respectively. Among the spontaneous emissions generated from these Ω states, those from the A1Σ–1 – a3Σ+0–, A1Σ–1 – a3Σ+1, B1Δ2 – b3Δ3, b3Δ2 – a3Σ+1, d3Σ–0+ – a3Σ+0–, and d3Σ–1 – a3Σ+1 transitions were relatively strong. The transition properties reported herein are expected to provide useful guidelines for the detection in future experiments.

Molecular opacities of low-lying states of oxygen molecule**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300), the National Natural Science Foundation of China (Grant Nos. 11934004, 11404180, and 11604052), and the China Postdoctoral Science Foundation (Grant No. 2018M631404).

The , A′3Δu, , 13Πg, and electronic states of oxygen molecule (O2) are calculated by the multi-configuration self-consisted filed (MRCI) + Q method with the scalar relativistic correction and core–valence correlation correction. The obtained spectroscopic constants of the low-lying bound states are in excellent agreement with measurements. Based on the accurately calculated structure parameters, the opacities of the oxygen molecule at the temperatures of 1000 K, 2000 K, 2500 K, and 5000 K under a pressure of 100 atm (1 atm = 1.01325 × 105 Pa) and the partition functions between 10 K and 104 K are obtained. It is found that with the increase of temperature, the opacities for transitions in a long wavelength range are enlarged because of the larger population on excited electronic states at the higher temperatures.

Vibronic emissions and radiative lifetimes for a3Σ+, b3Π, c3Σ+, d3Δ, and e 3Σ– states of silicon monoxide

In this study, the potential energy curves of the a3Σ+, b3Π, c3Σ+, d3Δ, and e3Σ– states of the silicon monoxide are calculated and the transition dipole moments between them are computed using the complete active space self–consistent field, which is followed by the valence internally contracted multireference configuration interaction approach. The Davidson correction, core–valence correlation and scalar relativistic corrections are considered. The extrapolation of the potential energies to the complete basis set limit is included. The band origins, Einstein A coefficients, and Franck–Condon factors of all vibronic emissions between these five states are calculated. The rotationless radiative lifetimes are approximately 10–1 to 10–4 s for the b3Π state, 10–2 to 10–4 s for the d3Δ state, and 10–3 to 10–4 s for the e3Σ– state. The radiative lifetime quickly becomes shorter as the vibrational level increases for the three states. The lifetime is of the order of 100 ns for all vibrational levels of the c3Σ+ state, indicating that the spontaneous vibronic emissions originating from this state occurs easily. Overall, the vibronic emissions of the b3Π – a3Σ+, d3Δ – b3Π, and e3Σ– – b3Π systems are weak, suggesting that they are difficult to measure through spectroscopy. The vibronic emissions of the c3Σ+ – a3Σ+ and c3Σ+ – b3Π systems are strong, indicating that they are easy to measure in a spectroscopy experiment. The radiative lifetime with the variation of rotational angular momentum quantum number is discussed briefly for υ ≤ 15 and J ≤ 30 of the b3Π, c3Σ+, d3Δ, and e3Σ– states. The results indicate that the radiative lifetime changes only over a small range for each triplet state. The transition properties calculated in this study can be used to explain why only a few experimental transition properties are currently available for these triplet states.

Transition Dipole Moments and Transition Probabilities of the CN Radical

Abstract This paper studies the transition probabilities of electric dipole transitions between 10 low-lying states of the CN radical. These states are X2Σ+, A2Π, B2Σ+, a4Σ+, b4Π, 14Σ−, 24Π, 14Δ, 16Σ+, and 16Π. The potential energy curves are calculated using the CASSCF method, which is followed by the icMRCI approach with the Davidson correction. The transition dipole moments between different states are calculated. To improve the accuracy of potential energy curves, core–valence correlation and scalar relativistic corrections, as well as the extrapolation of potential energies to the complete basis set limit are included. The Franck–Condon factors and Einstein coefficients of emissions are calculated. The radiative lifetimes are determined for the vibrational levels of the A2Π, B2Σ+, b4Π, 14Σ−, 24Π, 14Δ, and 16Π states. According to the transition probabilities and radiative lifetimes, some guidelines for detecting these states spectroscopically are proposed. The spin–orbit coupling effect on the spectroscopic and vibrational properties is evaluated. The splitting energy in the A2Π state is determined to be 50.99 cm−1, which compares well with the experimental ones. The potential energy curves, transition dipole moments, spectroscopic parameters, and transition probabilities reported in this paper can be considered to be very reliable. The results obtained here can be used as guidelines for detecting these transitions, in particular those that have not been measured in previous experiments or have not been observed in the Sun, comets, stellar atmospheres, dark interstellar clouds, and diffuse interstellar clouds.

Accurate potential energy curves, spectroscopic parameters, transition dipole moments, and transition probabilities of 21 low–lying states of the CO+ cation

This paper calculates the potential energy curves of 21 Λ–S and 42 Ω states, which arise from the first two dissociation asymptotes of the CO+ cation. The calculations are conducted using the complete active space self–consistent field method, which is followed by the valence internally contracted multireference configuration interaction approach with the Davidson correction. To improve the reliability and accuracy of the potential energy curves, core–valence correlation and scalar relativistic corrections, as well as the extrapolation of potential energies to the complete basis set limit are taken into account. The spectroscopic parameters and vibrational levels are determined. The spin–orbit coupling effect on the spectroscopic parameters and vibrational levels is evaluated. To better study the transition probabilities, the transition dipole moments are computed. The Franck–Condon factors and Einstein coefficients of some emissions are calculated. The radiative lifetimes are determined for a number of vibrational levels of several states. The transitions between different Λ–S states are evaluated. Spectroscopic routines for observing these states are proposed. The spectroscopic parameters, vibrational levels, transition dipole moments, and transition probabilities reported in this paper can be considered to be very reliable and can be used as guidelines for detecting these states in an appropriate spectroscopy experiment, especially for the states that were very difficult to observe or were not detected in previous experiments.

Multireference configuration interaction study of ground and low-lying excited states of the AlC radical

ABSTRACTThis work explored the spectroscopic parameters and vibrational properties of the 21 Λ–S and 42 Ω states of the AlC radical. The PECs were calculated with the CASSCF method, which was followed by the icMRCI+Q approach. The A4Π, a2Π, 52Π, 22Δ, and 12Φ states as well as the first well of B4Σ− state were inverted with the spin–orbit coupling (SOC) effect included; the 14Δ, 14Σ+, and 22Σ− states as well as the second wells of the B4Σ−, 22Σ+, 32Σ+, 42Π and 52Π states were weakly bound, which well depths were less than 650 cm−1; the B4Σ−, 22Σ+, 32Σ+, 42Π, 52Π, and 22Δ states had double wells and the second wells of these states except for B4Σ− had only several vibrational states; the avoided crossings existed between the 22Σ+ and 32Σ+ states, the 32Σ+ and 42Σ+ states, the B4Σ− and 34Σ− states, the 22Δ and 32Δ states, the 42Π and 52Π states, the 52Π and 62Π states, as well as the 24Π and 34Π states. The extrapolation scheme, core–valence correlation and scalar relativistic corrections were included. The spectroscopic parameters and vibrational properties were determined. The TDM curves between two different Λ–S states were calculated and Franck–Condon factors of some transitions were evaluated. The SOC effect on the spectroscopic and vibrational properties was evaluated.

Accurate spectroscopic calculations of the 22 Λ-S states and 60 Ω states of the PS+ cation

This work studied the potential energy curves of 22 Λ-S states, which were yielded from the first two dissociation limits, P(4Su)+S+(4Su) and P+(3Pg)+S(3Pg), of the PS+ cation. The potential energy curves were calculated employing the CASSCF method, which was followed by the internally contracted MRCI approach with Davidson correction. Core- valence correlation and scalar relativistic corrections as well as basis set extrapolation were included. Of these 22 Λ-S states, only the 35Σ+ state was repluse without the spin-orbit coupling effect, whereas the 35Σ+, 15Δ, 25Σ+, and 15Σ− states were repulse with the spin-orbit coupling effect accounted for. The 21Π and 23Π states had double wells, but the first well of the 23Π state had no vibrational levels and the first well of 21Π state had only one vibrational state. The avoided crossings were found between the 11Π and 21Π states and between the d3Π and 23Π states. The 25Σ+, 15Π, 15Δ, b3Δ, and c3Σ− states were inverted with the spin-orbit coupling effect taken into account. The 15Δ, 25Σ+, 15Σ−, and 21Π states were weakly bound. The spectroscopic properties were evaluated and compared with the experimental and other theoretical results. The Franck-Condon factors of some electronic transitions between different Λ-S states were determined. The vibrational levels of several states were predicted. The spin-orbit coupling effect on the spectroscopic parameters was discussed. Analyses show that the spectroscopic results obtained here can be expected to be reliably predicted ones.

Accurate ab initio potential energy curves and spectroscopic properties of the low-lying electronic states of OH− and SH− molecular anions

ABSTRACTMultireference configuration interaction method was used in order to generate accurate potential energy curves of the OH, SH, OH− and SH− electronic states correlating to the three lowest dissociation limits. These curves were used in addition with core–valence correlation and scalar relativistic corrections for the calculations of accurate spectroscopic constants of bound states, which generally are found in excellent agreement with best available experimental and theoretical values in the literature. The spin–orbit interactions between electronic states have been calculated for the cases in which the couplings were assumed to be responsible for perturbations and used to explain the predissociation of A2Σ+ state of OH and SH by dissociative states 14Σ−, 12Σ− and 1 4Π. Dipole moment functions were also computed along internuclear distances and used to explain polarity of these molecules in different calculated electronic states. In addition, stability and metastability of electronic states (X 1Σ+, A1Π and a3Π) of OH− and SH− molecular anions have been studied relatively to curves of neutral parent electronic states. Finally, we have computed adiabatic electron affinity of OH and SH and these values have been found in very good agreement with the best experimental values and resort as among the best achieved values.

Accurate spectroscopic calculations of 21 electronic states of ClO radical including transition properties

The potential energy curves were calculated for the 21 states (X2Π, A2Π, 32Π, 42Π, 52Π, 12Σ+, 22Σ+, 32Σ+, 12Σ−, 22Σ−, 32Σ−, 12Δ, 22Δ, 32Δ, 12Φ, 14Σ+, a4Σ−, 24Σ−, 14Π, 24Π and 14Δ), which originated from the two lowest dissociation channels of ClO radical. The calculations were done for internuclear separations approximately from 0.08 to 1.10nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV5Z basis set. Of these 21 states, the 14Π, 24Π, 32Δ, 42Π, 52Π, 12Φ, 32Σ+, 14Δ and 24Σ− states are repulsive. The 12Δ, 12Σ−, 14Σ+, 22Σ−, 12Σ+, 22Σ+, 22Δ and 32Σ− states are very weakly bound. Only the A2Π state has one barrier. The avoided crossing exists between the A2Π and the 32Π state. However, the avoided crossing does not generate any double wells. Core- valence correlation correction was accounted for at the level of an aug-cc-pCVQZ basis set. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pVQZ basis set. All the potential energy curves were extrapolated to the complete basis set limit. The spectroscopic parameters were determined. The 12Σ−, 22Σ−, 32Σ− and 14Σ+ states may be very difficult to be detected in an experiment, since each of these Λ-S states has only one or two vibrational states. The Franck-Condon factors and radiative lifetimes were calculated for several low vibrational levels of the A2Π - X2Π, 32Π - a4Σ−, 22Δ - a4Σ− and 32Σ− - 12Σ− transitions. The spin-orbit coupling effect on the spectroscopic parameters of the X2Π, A2Π, 32Π, a4Σ− and 22Σ+ states were discussed. The spectroscopic properties reported here can be expected to be reliably predicted ones.

These effects of spin–orbit coupling, core–valence correlation and scalar relativistic correction on spectroscopic calculations for PN+ cation

The potential energy curves (PECs) of 9 Λ-S states (X2Σ+, 14Σ+, 16Σ+, A2Π, 14Π, 16Π, 14Δ, 14Σ−, 24Π) and corresponding 28 Ω states of PN+ cation are calculated by the complete active space self-consistent field (CASSCF), which is followed by the internally contracted multireference configuration interaction (icMRCI) with Davidson modification. The calculation is taken into account these effects of spin–orbit coupling, core–valence correlation and scalar relativistic correction. These are found that the 24Π, 16Π and 14Σ− states possess double wells and two avoided crossings occur between the 16Π and 26Π states, the 24Π and 34Π states. Based on the PECs, the spectroscopic parameters are evaluated. And the transitions (transition dipole moments, Franck–Condon Factors and radiative lifetimes) from 16Π−1/2 and 24Π−1/2 (the first well of the two states) to the ground state X2Σ+1/2 are obtained in this paper. These effects of spin–orbit coupling, core–valence correlation and scalar relativistic correction on the spectroscopic calculations are analyzed.

Accurate spectroscopic constants of the lowest two electronic states in S2 molecule with explicitly correlated method**Project supported by the National Natural Science Foundation of China (Grand No. 11574114) and the Natural Science Foundation of Jilin Province, China (Grand No. 20150101003JC).

A computational scheme for accurate spectroscopic constants was presented in this work and applied to the lowest two electronic states of sulfur dimer. A high-level ab initio calculation utilizing explicitly correlated multireference configuration interaction method (MRCI-F12) was performed to compute the potential energy curves (PECs) of the ground triplet and first excited singlet a1Δg states of sulfur dimer with cc-pCVXZ-F12(X = T, Q) basis sets. The effects of Davidson modification, core–valence correlation correction, and scalar relativistic correction on the spectroscopic constants were examined. The vibration–rotation spectra of the two electronic states were provided. Our computational results show excellent agreement with existing available experimental values, and the errors of main spectroscopic constants are within 0.1% order of magnitude. The present computational scheme is cheap and accurate, which is expected for extensive investigations on the potential energy curves or surfaces of other molecular systems.

Accurate calculations on 20 Λ–S states of the BP radical: potential energy curves, spectroscopic parameters, and electronic transition properties

The potential energy curves of 20 Λ–S states of BP yeilded from the first two dissociation limits B(2Pu) + P(4Su) and B(2Pu) + P(2Du) have been calculated by the internally contracted multireference configuration interaction approach with the Davidson correction. Especially the core–valence correlation and scalar relativistic corrections are included in the present work. Potential energy curves are also extrapolated to the complete basis set limit. According to the potential energy curves, the spectroscopic parameters are determined and compared with those available in the literature. The convergent behavior of the present calculations is discussed with respect to the basis set and level of theory. Of the 20 states, the 23∑– and 33∑– states have the avoided crossings, which are very weakly bound ones, the 21∑–, and the 13Δ and 23Δ states possess a double well. Subsequently, the transition dipole moments, Franck–Condon factors, and radiative times of the transitions 31Π–b1Π, 23Δ–X3Π, 23∑––A3∑–, 33∑––A3∑–, and 15∑––15Π are calculated.

Accurate calculation of the potential energy curve and spectroscopic parameters of X2Σ+ state of 12Mg1H**Project supported by the National Natural Science Foundation of China (Grand Nos. 11147158, 91221301, and 11264020)

High level calculations on the ground state of 12Mg1H molecule have been performed using multi-reference configuration interaction (MRCI) method with the Davidson modification. The core–valence correlation and scalar relativistic corrections are included into the present calculations at the same time. The potential energy curve (PEC) of the ground state, all of the vibrational levels and spectroscopic parameters are fitted. The results show that the levels and spectroscopic parameters are in good agreement with the available experimental data. The analytical potential energy function (APEF) is also deduced from the calculated PEC using the Murrell–Sorbie (M–S) potential function. The present results can provide a helpful reference for the future spectroscopic experiments or dynamical calculations of the molecule.

A theoretical investigation of the S2+ cation in the gas phase

The potential energy curves (PECs) of 18 lowest energy Λ-S states of the S2+ cation have been calculated using the complete active space self-consistent field method followed by the internally contracted multireference configuration interaction approach with the Davidson modification. When spin−orbit coupling is computed using the Breit−Pauli Hamiltonian with the cc-pCVTZ basis set, the 18 Λ-S states split into 56 Ω components. To improve the quality of the PECs, core−valence correlation and scalar relativistic corrections are included. All PECs are extrapolated to the complete basis set limit. Based on the PECs obtained by the icMRCI+CV+DK+Q/(CBS-56) calculations, the spectroscopic parameters of 17 Λ-S bound states and 50 Ω bound states are obtained. The transitions (including the Franck−Condon factors and radiative lifetimes) from two low-lying states to the ground state are calculated for several low vibrational levels. Analyses show that the spectroscopic parameters reported here can be expected to be reliably predicted.

Accurate spectroscopic properties of 19 low-lying states of PCl radical including the electronic transition properties

The spectroscopic properties are in detail studied for the 11Σ−, 21Σ−, b1Σ+, c1Π, 21Π, 31Π, a1Δ, 21Δ, X3Σ−, C3Σ−, 33Σ−, 13Σ+, A3Π, B3Π, 33Π, 13Δ, 23Δ, 15Σ− and 15Π states, which are yielded from the first two dissociation limits, P(4Su)+Cl(2Pu) and P(2Du)+Cl(2Pu), of the PCl radical. Of the nineteen states, the 33Σ−, 13Σ+, 13Δ, 23Δ and 15Π states are the repulsive ones. The 21Σ−, 21Δ and 15Σ− states and the second well of A3Π state are very weakly-bound ones. The A3Π and B3Π states, the B3Π and 33Π states, and the 21Π and 31Π states have the avoided crossings. The A3Π state is found to possess the double well. The potential energy curves (PECs) are calculated with the CASSCF method followed by the internally contracted MRCI approach with Davidson correction together with the Dunning’s correlation-consistent basis sets, aug-cc-pV6Z. To improve the quality of PECs, core–valence correlation and scalar relativistic correction calculations are included simultaneously. The PECs are extrapolated to the complete basis set limit. The vibrational properties are evaluated for several weakly-bound states. The spectroscopic parameters are determined, and compared with those available in the literature. The Franck–Condon factors and radiative lifetimes of the transitions from the A3Π, B3Π and 33Π states to the X3Σ− state and from the c1Π, 21Π and 31Π states to the a1Δ state are calculated for several low vibrational states. And some necessary discussion is performed. Analyses demonstrate that the spectroscopic properties of PCl radical reported in this paper can be expected to be reliably predicted ones.

Extensive spectroscopic calculations of the 21 Λ-S and 74 Ω states of the AsN molecule including the spin–orbit coupling effect

The potential energy curves (PECs) of 74 Ω states generated from the 21 Λ-S states of AsN molecule are studied for the first time for internuclear separations from 0.1 to 1.0nm. Of these 21 Λ-S states, the X1Σ+, a′3Σ+, 15Σ+, 13Δ, 13Σ−, a3Π, 15Π, 25Σ+, 35Σ+, 23Δ, 23Π, 33Π, 35Π, and A1Π states are found to be bound, and the 23Σ+, 33Σ+, 15Σ−, 15Δ, 25Δ, 25Π, and 17Σ+ states are found to be repulsive ones. The 33Π state possesses the double well. The 25Σ+, 35Σ+, 35Π, and 33Π states possess the shallow well. The a′3Σ+, 13Σ−, 23Π, 13Δ, 15Π, 25Π, 35Π, and 17Σ+ states are found to be the inverted ones with the spin–orbit coupling effect taken into account. The PECs are calculated using the CASSCF method, which is followed by the internally contracted MRCI approach with Davidson correction. Core–valence correlation and scalar relativistic corrections are included. The vibrational properties are evaluated for the 25Σ+, 35Σ+, and 35Π states and the second well of the 33Π state. The spin–orbit coupling effect is accounted for by the state interaction method with the Breit–Pauli Hamiltonian. The PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated, and compared with available measurements and other theoretical results. The Franck–Condon factors and radiative lifetimes of the transitions from the a′3Σ+1, a3Π1, A1Π1, 13Δ1 and a3Π0− states to the X1Σ+0+ state are calculated for several low vibrational levels, and some necessary discussion is performed. Analyses show that the spectroscopic parameters reported in this paper can be expected to be reliably predicted ones.