Molecular constants of LiCl(X^1Σ^+) and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures

Interaction potentials for LiCI（X^1∑＋） are constructed by the highly accurate valence internally contracted multireference configuration interaction in combination with a number of large correlation-consistent basis sets, which are used to determine the spectroscopic parameters （D0, De, Re, ωe, ωeχe, Be and αe）. The potentials obtained at the basis sets, i.e., aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li, are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0 ×10^-12 to 1.0× 10-4 a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and their shapes are mainly dominated by the s-partial wave at very low impact energies. Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime, which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves. Abundant resonances exist for the elastic partial-wave cross sections until l= 22 partial waves. The vibrational manifolds of the LiCI（X^1∑＋） molecule, which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl, should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.

Theoretical investigations of spectroscopic parameters and molecular constants for electronic ground state of Cl_2 and its isotopes

The potential energy curve of the C12 （X1∑g＋） is investigated by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach in combination with the largest correlation-consistent basis set, aug-cc-pV6Z, in the valence range. The theoretical spectroscopic parameters and the molecular constants of three isotopes, 35Cl2, 35Cl37Cl and 37Cl2, are studied. For the 35Cl2（X1∑g＋）, the values of Do, De, Re, We, we）we, ae and Be are obtained to be 2.3921 eV, 2.4264 eV, 0.19939 nm, 555.13 cm-1, 2.6772 cm-1, 0.001481 cm-1 and 0.24225 cm-1, respectively. For the 356137Cl（X1∑g＋）, the values of Do, De, Re, We, WeXe, ae and Be are calculated to be 2.3918 eV, 2.4257 eV, 0.19939 nm, 547.68 cm-1, 2.6234 cm-1, 0.00140 cm^1 and 0.23572 cm-1, respectively. And for the 37Cl2（X1∑g＋）, the values of Do, De, Re, We, WeXe, ae and Be are obtained to be 2.3923 eV, 2.4257 eV, 0.19939 nm, 540.06 cm-1, 2.5556 cm-1, 0.00139 cm-1 and 0.22919 cm-1, respectively. These spectroscopic results are in good agreement with the available experimental data. With the potential of Cl2 molecule determined at the MRCI/aug-cc-pV6Z level of theory, the total of 59 vibrational states is predicted for each isotope when the rotational quantum number J equals zero （J = 0）. The theoretical vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0, which are in excellent accordance with the available experimental findings.

Spectroscopic parameters and molecular constants of HI(X^1Σ^+),DI(X^1Σ^+) and TI(X^1Σ^+) isotope molecules

The potential energy curve （PEC） of HI（X^1∑^＋） molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEG of HI（X^1∑^＋）, the spectroscopic parameters of three isotopes, HI（X1E＋）, DI（X^1∑^＋） and TI（X^1∑^＋）, are determined in the present work. For the HI（X^1∑^＋）, the values of Do, De, Re, ωe, ωeχe, αe and Be are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm^-1, 40.0703 cm^-1, 0.1699 cm^-1 and 6.4373 cm^-1, respectively; for the DI （X^1∑^＋）, the values of D0, De, Re, ωe, ωeχe, αe and Be are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm^-1, 20.8581 cm^-1, 0.0611 cm^-1 and 3.2468 cm^-1, respectively; for the TI （X^1∑^＋）, the values of Do, De, Re, ωe, ωeχe, αe and Be are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm^-1, 14.0765 cm^-1, 0.0338 cm^-1 and 2.1850 cm^-1, respectively. These results accord well with the available experimental results. With the PEC of HI（X^1∑^＋） molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero （J = 0）. For each vibrational state, vibrational level G（v）, inertial rotation constant By and centrifugal distortion constant Dv are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.

Investigations of spectroscopic parameters and molecular constants for X^1Σ_g^+, w^3△_u, and W^1△_u electronic states of P_2 molecule

The potential energy curves （PECs） of three low-lying electronic states （X1 ∑g^＋, w^3 △u, and W1 △u） of P2 molecule are investigated using the full valence complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach in conjunction with the correlation-consistent basis set in the valence range. The PECs of the electronic states involved are modified by the Davidson correction and extrapolated to the complete basis set （CBS） limit. With these PECs, the spectroscopic parameters of the three electronic states are determined and compared in detail with the experimental data. The comparison shows that excellent agreement exists between the present results and the available experimental data. The complete vibrational states are computed for the W3Au and WlAu electronic states when the rotational quantum number J equals zero and the vibrational level G（v）, the inertial rotation constant By, and the centrifugal distortion constant Dv of the first 30 vibrational states are reported, which accord well with the experimental data. The present results show that the two-point extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.

MRCI study of spectroscopic and molecular properties of X^1Σ_g^+ and A^1Π_u electronic states of the C_2 radical

The potential energy curves （PECs） of X^1∑g^＋ and A^1∏u electronic states of the C2 radical have been studied using the full valence complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRC1） approach in conjunction with the aug-cc-pV6Z basis set for internuclear separations from 0.08 nm to 1.66 nm. With these PECs of the C2 radical, the spectroscopic parameters of three isotopologues （^12C2, ^12C^13C and ^13C2） have been determined. Compared in detail with previous studies reported in the literature, excellent agreement has been found. The complete vibrational levels G（v）, inertial rotation constants By and centrifugal distortion constants D, for the ^12C2, ^12C^13C and ^13C2 isotopologues have been calculated for the first time for the X^1∑g^＋ and A^1∏u electronic states when the rotational quantum number J equals zero. The results are in excellent agreement with previous experimental data in the literature, which shows that the presented molecular constants in this paper are reliable and accurate.

Optical spectroscopy of CrO and electronic states of the Cr group metal monoxides

All of the experimentally known electronic states of the Cr group metal monoxides(Cr O,Mo O,and WO)have been presented in the paper.The optical spectra of the Cr O molecule have been investigated in the gas phase through a combination of the laser-induced fluorescence(LIF)excitation and single-vibronic-level(SVL)emission spectroscopy in the supersonic expansion.The rotational constants of the vibronic electronic states,including X^(5)Π_(-1)(v=0–3),B^(5)Π_(-1)(v=0–10),and B~5Π_1(v=1,5),and the vibrational constants of the spin–orbit components X^(5)Π_(-1,0,1)have been obtained.The molecular constants of the Mo O and WO molecules have been summarized by reviewing the previous spectroscopic studies,and a comprehensive energy level diagram of the Cr group metal monoxides has been constructed.By comparing the electronic configurations,bond lengths,and vibrational frequencies of all the transition metal monoxides in the ground electronic state,the significance of the relativistic effect in the bonding of the 5d transition metal monoxides has been discussed.The related spectroscopic data of the Cr O molecule are available at https://doi.org/10.57760/sciencedb.j00113.00085.

Study on the A^2Π_(3/2u), B^2Δ_(3/2u), and X^2Π_(3/2g) states of Cl_2^+ including its isotopologues

Adopting the experimentally available vibrational constants in a recent analysis of the strong perturbation between the A22Π3/2u and BΔ3/2u states of Cl+2in the A–X band system [Gharaibeh et al. 2012 J. Chem. Phys. 137 194317], an unambiguous vibrational assignment of the bands reported previously is carried out. The equilibrium rotational constants Be and α e of the X2Π3/2g and A2Π3/2u states for35Cl+2and35Cl37Cl+and those of the B2Δ3/2u state for35Cl+2are obtained by fitting the experimental values of Bυ. In addition, the values of Be and α e of these three states for the minor isotopologues35Cl37Cl+and37Cl+2are predicted by employing the isotopic effect. The values of equilibrium internuclear distance Re of the three states for the three isotopologues are calculated as well.

Isotopic effect of Cl_2^+ rovibronic spectra in the A-X system

This paper studies the isotopic effect of Cl2^＋ rovibronic spectra in the A^2Лu （Ω = 1/2）-X^2Лg （Ω = 1/2） system. Based on the experimental results of the molecular constants of ^35Cl2^＋, it calculates the vibrational isotope shifts of the （2, 7） and （3, 7） band between the isotopic species ^35C12^＋, ^35Cl^37Cl ＋ and ^37Cl2^＋, and estimates the rotational constants of both A^2Лu and X^2Лg states for the minor isotopic species ^35Cl^37Cl＋ and ^37Cl2^＋. The experimental results of the spectrum of 35Cl37Cl-1- （3, 7） band proves the above mentioned theoretical calculation. The molecular constants and thus resultant rovibronic spectrum for ^37Cl2^＋ were predicted, which will be helpful for further experimental investigation.

The Nature of Bonding in WC and WN

The nature of bonding in the title compounds has been studied by using CASSCF and FOCI techniques. The ground states of WC and WN are found to be 3Δ and 4∑- state arising primarily from:...1(22(21(41(13(1 and ...1(22(21(41(23(1 configuration respectively. WC shows a strong character of covalent bond while WN have obvious character of ionic bond and the dissociation energy of WN is larger than that of WC (6.15 and 5.41 eV respective).

The Nature of Bonding in PtC and PtN

The nature of bonding in the title compounds has been studied by using CASSCF and FOCI techniques. The ground states of PtC and PtN are found to be (1)Sigma (+) and (2)Pi state arising primarily from:... 1 sigma (2)2 sigma (2)1 pi (4)1 delta (4)3 sigma (2) and...1 sigma (2)2 sigma (2)1 pi (4)1 delta (4)3 sigma (2)2 pi (1) configuration respectively and both of which form triple bond tone sigma, two pi bonds), but the bond of PtC is much stronger than that of PtN.

Accurate ab initio study of low-lying electronic states of phosphorus nitride radical

This paper employs the highly accurate valence internally contracted multireference configuration interaction method to investigate the potential energy curves （PECs） for the ground state （X^1 ∑^＋） and two low-lying excited states （A^1∏ and D^1 △ of phosphorus nitride （PN） radical with the correlation-consistent basis set, aug-cc-pV6Z, in the valence range. Relativistic effects are considered in these calculations. The spectroscopic constants of the X^1 ∑^＋ and A^1∏ states are calculated based on the PECs, and the results are in good accord with the available experimental data. The first 30 vibrational states for the X^1 ∑^＋ state and the first 40 vibrational states for the A^1∏ state are determined when J = 0. For each vibrational state, molecular constants G（v）, B（v） and D（v） are also attained.

The Nature of Bonding in IrC

The nature of bonding in the title compound has been stUdied by using CASSCF andFOCI techniques. The ground state of IrC has been found to be 2△ arising primarilyfrom:.. 1σ2 2σ2 1π4 1δ3 3σ2 configuration, which forms a triple bond between Ir and C atoms (one σ;two π). The lowest quartet state is 4Φ state which has the configuration:... 1σ2 2σ2 1π4 1δ3 2π1 3σ2 andlies higher than the ground state by 1 .25eV. The molecular constants of the ground state calculatedat CASSCF level by using Morse's mode are: Re=1.6904A, De=4.86eV, We=1139cm-1, andB0=0.5219cm-1 comparable with the spectrum values (Re=1 .6858A, De=6.44 eV, We=1051cm-1and B0=0.5251 cm-1).

Global analysis of the Comet-tail system of ^(12)C^(16)O^+

A global analysis of the ro-vibrational spectra of 19 bands in the comet-tail （A2Πi-X2Σ＋） system of the 12C16O＋ cation is presented, and the precise molecular constants of the vibrational levels involved are obtained via a weighted nonlinear least-squares fitting procedure. Furthermore, the resultant precise equilibrium molecular constants enable us to achieve accurate Rydberg-Klein-Rees （RKR） potential curves for both the A and X states, yielding the accurate Franck-Condon factor and band origin of each band in this system.

Absorption spectra and isotope shifts of the(2, 0),(3, 1), and(8, 5) bands of the A^2Π_u-X^2Σ_g^+ system of ^(15)N_2^+ in near infrared

The high-resolution absorption spectra of the （2,0）,（3,1）,and （8,5） bands of the A^2Π^u-X^2∑g^＋ system of ^15N2^＋ have been recorded by using velocity modulation spectroscopy technique in the near infrared region.The rotational constants of the X^2∑g^＋ and A^2Πu states of ^15N2^＋ were derived from the spectroscopic data.The isotope shifts of these bands of the A^2Πu-X^2∑g^＋ system of ^14N2^＋ and ^15N2^＋ were also analyzed and discussed.

Accurate potential energy function and spectroscopic study of the X^2Σ^+,A^2Ⅱ and B^2Σ^+ states of the CP radical

This paper calculates the equilibrium internuclear separations, the harmonic frequencies and the potential energy curves of the X^2∑＋, A^2П and B^2∑＋ states of the CP radical by the highly accurate valence internally contracted multireference configuration interaction method with correlation-consistent basis sets （aug-cc-pV6Z for C atom and aug-cc-pVQZ for P atom）. The potential energy curves are all fitted with the analytic potential energy function by the least-square fitting. Employing the analytic potential energy function, we determine the spectroscopic constants （Be, αe and ωeχe） of these states. For the X2∑＋ state, the obtained values of De, Be, αe, ωeχe, Re and ωe are 5.4831 eV, 0.792119 cm-1, 0.005521 cm-1, 6.89653 cm-1, 0.15683 nm, 12535.11 cm-1, respectively. For the A2H state, the present values of De, Be,αe, ωeχe, Re and We are 4.586 eV, 0.703333 cm-1, 0.005458 cm-1, 6.03398 cm-1, 0.16613 nm, 1057.89 cm-1, respectively. For the B2E＋ state, the present values of De, Be, αe, ωeχe, Re and We are 3.506 eV, 0.677561 cm-1, 0.00603298 cm-1, 5.68809 cm-1, 0.1696 nm, 822.554 cm-1, respectively. For these states, the vibrational states with the rotational quantum number J equals zero （J = 0） are studied by solving the radial nuclear Schr6dinger equation using the Numerov method. For each vibrational state, the vibrational level, the classical turning points, the rotational inertial and the centrifugal distortion constants are calculated. Comparison is made with recent theoretical and experimental results.

Effects of urea,metal ions and surfactants on the binding of baicalein with bovine serum albumin

The interaction of baicalein with bovine serum albumin（BSA） was investigated with the help of spectroscopic and molecular docking studies.The binding affinity of baicalein towards BSA was estimated to be in order of 10~5 M^（-1） from fluorescence quenching studies.Negative ΔH°（-5.66 ＋ 0.14 kJ/mol） and positive（ΔS°）（＋ 79.96 ＋ 0.65J/mol K） indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positive ΔS°.The hydrophobic association of baicalein with BSA diminishes in the presence of sodium dodecyl sulfate（SDS） due to probable hydrophobic association of baicalein with SDS,resulting in a negative ΔS°（-40.65 ＋ 0.87 J/mol K）.Matrix-assisted laser desorption ionization/time of flight（MALDI-TOF） experiments indicate a 1：1 complexation between baicalein and BSA.The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements.It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA.The presence of metal ions（Ag~＋,Mg^（2＋）,Ni^（2＋）,Mn^（2＋）,Co^（2＋） and Zn^（2＋）） increased the binding affinity of ligand towards BSA.The changes in conformational aspects of BSA after ligand binding were also investigated using circular dichroism（CD） and Fourier transform infrared（FT-IR） spectroscopic techniques.Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1（subdomain MA） of BSA.

Elastic Collisions Between two Ground-State P and D Atoms at Low and Ultralow Temperatures

The PD（X^3∑^-） interaction potential is constructed using the CCSD（T） theory and the basis set, augcc-pV5Z. Using this potential, the spectroscopic parameters are accurately determined. The present Do, De, Re, ωe, ωeχe, αe, and Be are of 3.056 99 eV, 3.161 75 eV, 0.142 39 nm, 1701.558 cm^-1, 23.6583 cm^-1, 0.085 99 cm^-1, and 4.3963 cm^-1, respectively, which almost perfectly conform with the measurements. A total of 26 vibrational states is predicted when J = 0 by solving the radial Sehrodinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which favorably agree with the experiments. The total and various partial-wave cross sections are calculated for the elastic impact between two ground-state P and D atoms at 1.0 × 10^-12 - 1.0 × 10^-4 a.u. when they approach each other along the PD（X^3∑^-） potential. No shape resonances exist in the total elastic cross sections, though the peaks can be found for each partial wave until l=6. The shape of the total elastic cross sections is dominated by the s partial wave at very low temperatures. Due to the weakness of the shape resonances of each partial wave, they are all passed into oblivion by the strong total elastic cross sections.

Multireference configuration interaction study on spectroscopic properties of low-lying electronic states of As_2 molecule

The potential energy curves （PECs） of four electronic states （X^1∑g＋, e^3△u, a3∑^-u, and d3Лg） of an As2 molecule are investigated employing the complete active space self-consistent field （CASSCF） method followed by the valence internally contracted multireference configuration interaction （MRCI） approach in conjunction with the correlation-consistent aug-cc- pV5Z basis set. The effect on PECs by the relativistic correction is taken into account. The way to consider the relativistic correction is to employ the second-order Douglas-Kroll Hamiltonian approximation. The correction is made at the level of a cc-pVSZ basis set. The PECs of the electronic states involved are extrapolated to the complete basis set limit. With the PECs, the spectroscopic parameters （Te, Re, ωe, ωeXe, ωeye, ae, βe, γe, and Be） of these electronic states are determined and compared in detail with those reported in the literature. Excellent agreement is found between the present results and the experimental data. The first 40 vibrational states are studied for each electronic state when the rotational quantum number J equals zero. In addition, the vibrational levels, inertial rotation and centrifugal distortion constants of d3Hg electronic state are reported which are in excellent agreement with the available measurements. Comparison with the experimental data shows that the present results are both reliable and accurate.

Theoretical Study on the Potential Energy Curve and Vibration-rotation Spectra of BeF Radical

The potential energy curve （PEC） of BeF（X2Σ＋） radical is investigated by using the complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach over the internuclear separation range from 0.0522 to 2.0472 nm. The PEC is fitted to the analytic Murrell-Sorbie function, which is employed to accurately determine the spectroscopic parameters. The present D0, De, Re, ωe, ωeχe, αe and Be are 6.14 eV, 6.22 eV, 0.1372 nm, 1236.12 cm-1, 9.11 cm-1, 0.0175 cm-1 and 1.4651 cm-1, respectively. These parameters have been compared with those of previous investigations reported in the literature. With PEC determined at the present level of theory, a total of 75 vibrational states have been predicted for the first time by numerically solving the radial Schrdinger equation of nuclear motion using the Numerov method. For each vibrational state, the complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined for the first time. Comparing with the available experiments and other theories, we find that the present spectroscopic parameter and molecular constant results are more accurate and complete than the previous theoretical investigations.

Micellar Exchange Kinetics of Quaternary Ammonium Type Gemini Surfactants Monitored by Nuclear Magnetic Resonance

The dynamic NMR （DNMR） method was used to detect kinetic parameters of the molecular exchange process between monomers in bulk solution and those in the micelle for Gemini surfactants, 12-s-12 and 14-s-14 （s 2, 3 and 4）. The escape rate constant, k^- , was derived based on the simplified equations of DNMR theory, and the apparent activation energy of escape, Ea^- , was obtained based on the Arrhenius equation through temperature variation experiments. Results show that the orders of magnitude of k^- for 14-s-14 and 12-s-12 are respectively 10 and 103 s-1, Ea^- of 14-s-14 and 12-s-12 are respectively 54.04-73.64 and 33.42-47.09 kJ/rnol. Furthermore, k increases and Ea^- decreases with the spacer length growing. In combination with the rnicro-polarity measurements, it was revealed that molecules of 14-s-14 and 12-s-12 have to experience conformation changes when escaping from the rnicelles. The two-step molecular exchange mechanism for Gemini surfactants was therefore supported.