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.

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.

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.

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.

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.

Thermal Analysis of Thermophysical Data for Equilibrium Pure Fluids

The thermal analysis of precise thermophysical data for pure fluids from electronic databases is developed to investigate the molecular interaction mechanisms and parameters and the structural features of heterogeneities in fluids. The method is based on the series expansion of thermophysical values by powers of the monomer fraction density. Unlike the virial expansion by powers of the total density, the series expansion terms in this method directly reflect properties of the corresponding cluster fractions. The internal energy had been selected among thermophysical properties as the most informative for this method. The thermal analysis of its series expansion coefficients permits to estimate the temperature dependence of the pair bond parameters, the clusters’ bond energies and equilibrium constants, the structural transitions between dominating isomers of clusters. The application of method to different pure fluids, including noble and molecular gases with van der Waals and polar molecular interactions, brings unknown clusters’ characteristics for the fluids under investigation. The thermal analysis of the ordinary and heavy Water vapors points on no trivial isotopic effects. The unpredictable growth of the pair bond energy with temperature in Alkanes points on existence in hydrocarbons of some unknown molecular interaction forces in addition to dispersion forces.

从头算方法研究SO_3分子的光谱常数

本文用从头算方法中的二阶多体微扰理论MP2以及密度泛函理论中的B3LYP和B3PW91方法结合cc-p VTZ基组计算了SO_3同位素分子(^(32)S^(16)O_3、^(32)S^(18)O_3、^(34)S^(16)O_3、^(34)S^(18)O_3)的平衡结构以及振动和转动光谱常数.分析同位素取代对四个谐振频率的影响.将计算的光谱常数与实验结果相比较,并预测了SO_3分子的偶极矩.通过分析计算结果可以得出B3PW91方法计算的结果与实验结果符合得最好.