Intra-and Intermolecular Rovibrational States of HCl-H_(2)O and DCl-H_(2)O Dimers from Full-Dimensional and Fully Coupled Quantum Calculations

We report full-dimensional and fully coupled quantum bound-state calculations of the J=1 intra-and intermolecular rovibrational states of two isotopologues of the hydrogen chloride-water dimer,HClH_(2)O(HH)and DCl-H_(2)O(DH).The present study complements our recent theoretical investigations of the J=0 nine-dimensional(9D)vibrational level structure of these and two other H/D isotopologues of this noncovalently bound molecular complex,and employs the same accurate 9D permutation invariant polynomial-neural network potential energy surface.The calculations yield all intramolecular vibrational fundamentals of the HH and DH dimers and the low-energy intermolecular rovibrational states in these intramolecular vibrational manifolds.The results are compared with those of the 9D J=0 calculations of the same dimers.The energy differences between the K=1 and K=0 eigenstates exhibit pronounced variations with the intermolecular rovibrational states,for which a qualitative explanation is provided.

Using <i>ScalIT</i>for Performing Accurate Rovibrational Spectroscopy Calculations for Triatomic Molecules: A Practical Guide

This paper presents a practical guide for use of the ScalIT software package to perform highly accurate bound rovibrational spectroscopy calculations for triatomic molecules. At its core, ScalIT serves as a massively scalable iterative sparse matrix solver, while assisting modules serve to create rovibrational Hamiltonian matrices, and analyze computed energy levels (eigenvalues) and wavefunctions (eigenvectors). Some of the methods incorporated into the package include: phase space optimized discrete variable representation, preconditioned inexact spectral transform, and optimal separable basis preconditioning. ScalIT has previously been implemented successfully for a wide range of chemical applications, allowing even the most state-of-the-art calculations to be computed with relative ease, across a large number of computational cores, in a short amount of time.

Theoretical Study with Rovibrational and Dipole Moment Calculation of the SiO Molecule

Via CASSCF/MRCI and RSPT2 calculations (single and double excitation with Davidson correction) the potential en- ergy curves of 20 electronic states in the representation 2S+1Λ(±)of the molecule SiO have been calculated. By fitting these potential energy curves to a polynomial around the equilibrium internuclear distance re, the harmonic frequency ωe, the rotational constant Be, and the electronic energy with respect to the ground state Te have been calculated. For the considered electronic states the permanent dipole moment μ have been plotted versus the internuclear distance r. Based on the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points rmin and rmax have been calculated. The comparison of these values to the experimental and theoretical results available in the literature is presented. In the present work 8 higher electronic states have been studied theoretically for the first time.

Electronic Structure with Rovibrationl and Dipole Moment Study of the NiO Molecule

The potential energy curves have been investigated for the 40 lowest electronic states in the 2s+1Λ(±)representation below 25000 cm-1 of the molecule NiO via CASSCF, MRCI (single and double excitation with Davidson correction) and CASPT2 methods. The harmonic frequency ωe , the internuclear distance re, the rotational constant Be, the electronic energy with respect to the ground state Te, and the permanent dipole moment μ have been calculated. By using the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points rmin and rmax have been calculated for the considered electronic states up to the vibration level v = 12. Eleven electronic states have been studied theoretically here for the first time. The comparison of these values to the theoretical and experimental results available in literature shows a very good agreement.

A new exact quantum mechanical rovibrational kinetic energy operator for penta-atomic systems in internal coordinates

The concrete molecule-fixed (MF) kinetic energy operator for penta-atomic molecules is expressed in terms of the parameter δ, the matrix element Gij, and angular momentum operatorj. The applications of the operator are also discussed. Finally, a general compact form of kinetic energy operator suitable for calculating the rovibrational spectra of polyatomic molecules is presented.

Method for studying diatomic rovibrational spectra at a given vibrational state

An algebraic method for rotational energies at a given vibrational state(AMr(v)) is proposed in this study in order to obtain unknown high-lying rovibrational energies. Applications of this method to the ground electronic state X^1Σ^+of CO and the excited state C^1Σ^+of^(39)K^7Li molecules show the following:(1) the AMr(v) can give the rational upper limit J of a rotational quantum number of a diatomic electronic state;(2) the full AMr(v) rovibrational energies {E_(υJ)}_υ of given vibrational states not only reproduce all known experimental data excellently but also predict precisely the values of all high-lying rovibrational energies,which may not be available experimentally.

Hadron resonances as rovibrational states

A rovibrational model,including anharmonic,centrifugal,and Coriolis corrections,is used to calculate π,K,N,and ∑ orbital and radial resonances.The four orbital excitations of the n meson correspond to the/?(1235),ti2(1670),63(2030),and π4(2250)resonances.Its first four radial excitations correspond to the π(1300),π(1800),π(2070),and 7t(2360)resonances.The orbital excitations of the K meson are interpreted as the K_(1)(1270),K_(2)(1770),K_(3)(2320),and K_(4)(2500)resonances;its radial excitations correspond to the K(1460)and K(1830)resonances.The N orbital excitations are identified with the N(1520),N(1680),N(2190),N(2220),and N(2600)resonances.The first four radial excitations of the N family correspond to the N(1440),N(1880),N(2100),and N(2300)resonances.The orbital excitations of the ∑ baryon are associated with the ∑(1670),∑(1915),∑(2100),and ∑(2250)resonances,whereas its radial excitations are identified with the ∑(1660),∑(1770),and ∑(1880)resonances.The proposed rovibrational model calculations show a good agreement with the corresponding experimental values and allow for the prediction of hadron resonances,thereby proving to be useful for the interpretation of excited hadron spectra.

Formation of NaH Molecules in the Lowest Rovibrational Level of the Ground Electronic State via Short-Range Photoassociation

The formation of NaH molecules in the lowest rovibrational level of the ground electronic state is investigated using a pump-dump photoassociation(PA)scheme.In short-range region,two colliding atoms Na and H are efficiently associated into the NaH molecule in the rovibrational|0,0i state of the ground electronic state via the intermediately rovibrational|10,1i state of the excited electronic state.The changes of populations with the electric field amplitudes,frequency detunings,dump pulse duration and delay time between two laser pulses are calculated and discussed.The PA probability reaches 0.623 with a high state-selectivity.

High-precision spectroscopy of hydrogen molecular ions

In this paper, we overview recent advances in high-precision structure calculations of the hydrogen molecular ions （H2＋ and HD＋）, including nonrelativistic energy eigenvalues and relativistic and quantum electrodynamic corrections. In combination with high-precision measurements, it is feasible to precisely determine a molecular-based value of the proton- to-electron mass ratio. An experimental scheme is presented for measuring the rovibrational transition frequency （v,L） ： （0, 0） → （6,1） in HD＋, which is currently underway at the Wuhan Institute of Physics and Mathematics.

Photoassociation of ultracold RbCs molecules into the (2)0^- state (v = 189, 190) below the 5S_(1/2) + 6P_(1/2) dissociation limit

Ultracold polar RbCs molecules are produced via photoassociation in a laser-cooled mixture of ^85Rb and ^133Cs atoms. The a3∑＋ state molecules which decay from electronically excited （2）0- state RbCs molecules are detected by resonance- enhanced two-photon ionization. The new rovibrational levels （v = 189, 190） in the （2）0- state are also observed, which exist in theory and have not been observed in experiments yet. The corresponding rotational constants are measured by photoassociation spectroscopy, which are consistent with theoretical calculations using a nonrigid rotor model.

Infrared diode laser spectroscopy of O_2–N_2O van der Waals complex in the v_1 symmetric stretch region of N_2O

The rovibrational spectrum of O2–N2O van der Waals complex is measured in the ν1 symmetric stretch region of N2 O monomer using a tunable diode laser spectrometer. The complex is generated by a slit-pulsed supersonic expansion with gas mixtures of O2, N2 O, and He. Both a- and b-type transitions are observed. The effective Hamiltonian for an open-shell complex consisting of a diatomic molecule in a ^3Σ electronic state and a closed-shell partner is used to analyze the observed spectrum. Molecular constants in the vibrationally excited state are determined accurately. The band-origin of the spectrum is determined to be 1284.7504（25） cm^-1, red-shifted from that of the N2 O monomer by ～ 0.1529 cm^-1.

The Role of High Excitations in Constructing Sub-spectroscopic Accuracy Intermolecular Potential of He-HCN： Critically Examined by the High-Resolution Spectra with Resonance States

Interpreting high-resolution rovibrational spectra of weakly bound complexes commonly requires spectroscopic accuracy （〈1 cm-1） potential energy surfaces （PES）. Constructing high-accuracy ab initio PES relies on the high-level electronic structure approaches and the accurate physical models to represent the potentials. The coupled cluster approaches including single and double excitations with a perturbational estimate of triple excitations （CCSD（T）） have been termed the ＂gold standard＂ of electronic structure theory, and widely used in generating intermolecular interaction energies for most van der Waals complexes. However, for HCN-He complex, the observed millimeter-wave spectroscopy with high-excited resonance states has not been assigned and interpreted even on the ab initio PES computed at CCSD（T） level of theory with the complete basis set （CBS） limit. In this work, an effective three-dimensional ab initio PES for HCN-He, which explicitly incorporates dependence on the Q1 （C-H） normal-mode coordinate of the HCN monomer has been calculated at the CCSD（T）/CBS level. The post-CCSD（T） interaction energy has been examined and included in our PES. Analytic two-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for v1 （C-H）=0, and 1 to the Morse/Long-Range potential function form with root-mean-square deviations （RMSD） smaller than 0.011 cm-1. The role and significance of the post-CCSD（T） interaction energy contribution are clearly illustrated by comparison with the predicted rovibrational energy levels. With or without post-CCSD（T） corrections, the value of dissociation limit （Do） is 8.919 or 9.403 cm-1, respectively. The predicted millimeter-wave transitions and intensities from the PES with post-CCSD（T） excitation corrections are in good agreement with the available experimental data with RMS discrepancy of 0.072 cm-1. Moreover, the infrared spectrum for HCN-He complex is predicted for the first time. These results will serve as a good starting point and provide reliable guidance for future infrared studies of HCN doped in （He）n clusters.

Three-Dimensional Ab Initio Potential Energy Surface and Predicted Spectra for the CH_(4)-Ne Complex

We present a new three-dimensional potential energy surface(PES)for CH_(4)-Ne complex.The electronic structure computations were carried out using the coupled-cluster method with singles,doubles,and perturbative triples[CCSD(T)],the augmented correlationconsistent aug-cc-pVXZ(X=T,Q)basis sets were employed with bond functions placed at the mid-point on the intermolecular axis,and the energies obtained were then extrapolated to the complete basis set limit.Analytic intermolecular PES is obtained by least-squares fitting to the Morse/Long-Range(MLR)potential function form.These fits to 664 points have root-mean-square deviations of 0.042 cm^(−1).The bound rovibrational levels are calculated for the first time,and the predicted infrared spectra are in good agreement with the experimental values.The microwave spectra for CH_(4)-Ne dimer have also been predicted for the first time.The analytic PES can be used for modeling the dynamical behavior in CH_(4)-(Ne)N clusters,and it will be useful for future studies of the collision-induced-absorption for the CH_(4)-Ne dimer.

Theoretical Calculation of the Low-Lying Electronic States of the Molecule PbO

The potential energy curves of the lowest 20 electronic states in the representation 2s+1Λ(±) of the molecule PbO have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated along with the permanent dipole moment for the different bound investigated electronic states. By using the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points Rmin and Rmax have been calculated. The comparison of these values with those available in the literature shows a very good agreement.

Energy transfer reaction of metastable molecule CO(a) with NO in the beam experiment

The reaction of excited molecules and free radicals plays an important role in atmospheric chemistry, chemical laser and combustion process. The energy transfer reaction of metastable molecules N2（A）, CO（a） with diatomic molecules or free radicals has been paid great attention to for several years. However, the energy transfer reaction of CO（a） has not been extensively studied because of the difficulty in producing CO （a） with

Energy Transfer Reactions of Nitric Oxide With Rare Gas Metastable Atoms

Diatomic molecule NO is one of the most important compounds in atomospheric chemistry and environmental science. The study of its reactions, energy, transfer and dissociation process has been paid great attention to for practical importance. Much dynamical information is available concerning the E-E energy transfer reactions of NO with low energy metastable molecules N2（A） and CO（a）. Because the energy of rare gas metastable atoms He （23S）, Ne (3P0.2) and Ar (3P0.2) is much higher than theionization energy of NO molecules,the ionization and dissociation are the major channels in the reaction of NO with Rg*. Coxon et al. have studied the reaction ofHe（23S） with NO in flowing after-glow apparatus. The dissociative excitation and penning ionization channels were investigated by emission spectrometry, but the energy transfer process which is a minor channel （fraction【1%） was not discernable in their work.In this work, the authors used the electric discharge nozzle source to

Free Rotor Model or Rigid Rotor Model for CH3F-Ne Complex and Comparison with Other CH3F-Rare Gas Systems

The assignment of the rovibrational spectra of molecule-Ne complexes is always a challenge to study van der Waals systems, since they usually exhibit behavior intermediate between free rotor and rigid rotor. In this paper, the microwave and infrared spectra of CH3F-Ne, a model system for symmetric-top-atom dimer, were firstly pre- dicted and analyzed based on the four-dimensional ab initio intermolecular potential energy surfaces（PESs）, which explicitly incorporate the v3（C--F） stretch normal model coordinate of the CH3F monomer. Analytic three-dimensional PESs were obtained by least-squares fitting vibrationally averaged interaction energies for v3（CH3F）=0 and 1 to the Morse/long-range（MLR） potential function for symmetry top impurity with atom model. These PESs fitting to 2340 points have root-mean-square（RMS） deviations of 0.07 cm1, and require only 167 parameters. Based on the analytical vibrationally averaged PESs, the rovibrational energy levels were calculated by employing Lanczos algorithm, with combined radial discrete variable representation and parity-adapted angular finite basis representation. Based on the wavefunction analysis and comparison of CH3F-Ne with CH3F-He and CH3F-Ar complexes, the bound states were assigned. Spectral parameters for CH3F-Rg（Rg： rare gas, Rg=He, Ne, Ar） complexes were fitted and discussed. Temperature dependent transition intensities for CH3F-Ne were also reported and analyzed. The complete microwave and infrared spectra information for CH3F-Ne made it possible to provide important guidance for future experimental spectroscopic assignments.

Ionization process of collision of Ne( ~3P_(0,2)) with CO undermolecular beam condition

The ionization of CO with metastable Ne( 3P 0,2) in a molecular beam was studied by measuring the emission spectra of CO +(A 2Π i -X 2Σ +). The nascent vibrational and rotational distributions of CO +(A) were calculated by spectral simulation and the results are discussed.

Application of Lie algebraic method to the calculation of rotational spectra for linear triatomic molecules

The Hamiltonian describing rotational spectra of linear triatomic molecules has been derived by using the dynamical Lie algebra of symmetry group U1(4)?U24. After rovibrational interactions being considered, the eigenvalue expression of the Hamiltonian has the form of term value equation commonly used in spectrum analysis. The molecular rotational constants can be obtained by using the expression and fitting it to the observed lines. As an example, the rotational levels ofv 2 band for transition (0200–0110) of molecules N2O and HCN have been fitted and the fitting root-mean-square errors (RMS) are 0.00001 and 0.0014 cm?1, respectively.