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.

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.

A molecular dynamics study of the swelling patterns of Na/Cs-montmorillonites and the hydration of interlayer cations

We report on a molecular dynamics study of the swelling patterns of an Na-rich/Cs-poor montomorillonite and a Csmontomorillonite.The recently developed CLAYFF force field is used to predict the basal spacing as a function of the water content in the interlayer.The simulations reproduce the swelling patterns of the Na and Cs-montomorillonite,suggesting a mechanism of its hydration different from that of the montomorillonite.In addition,we find that the differences in size and hydration energy of Na and Cs ions have strong implications for the structure and the internal energy of interlayer water.In particular,our results indicate that the hydrate difference in the presence of coexistent Na and Cs has a larger influence on the behavior of a clay-water system.For Na-rich/Cs-poor montomorillonite,the hydration energy values of Na ions and water molecules each have a dramatic increase compared with those in Na-montomorillonite on the interlayer spacing,and the hydration energy values of Cs ions and water molecules decrease somewhat compared with those in Cs-montomorillonite.

Effects of signal modulation and coloured cross-correlation of coloured noises on the diffusion of a harmonic oscillator

The diffusion in a harmonic oscillator driven by coloured noises ξ（t） and η（t） with coloured cross-correlation in which one of the noises is modulated by a biased periodic signal is investigated. The exact expression of diffusion coefficient d as a function of noise parameter, signal parameter, and oscillator frequency is derived. The findings in this paper are as follows. 1） The curves of d versus noise intensity D and d versus noises cross-correlation time z3 exist as two different phases. The transition between the two phases arises from the change of the cross-correlation coefficient A of the two Ornstein-Uhlenbeck （O-U） noises. 2） Changing the value of T3, the curves of d versus Q, the intensity of colored noise that is modulated by the signal, can transform from a phase having a minimum to a monotonic phase. 3） Changing the value of signal amplitude A, d versus Q curves can transform from a phase having a minimum to a monotonic phase. The above-mentioned results demonstrate that a like noise-induced transition appears in the model.

Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

By adding frequency modulated signals to the intensity equation of gain noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio （SNR） of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.