NaC分子基态及其低电子激发态

运用包含Davidson修正的多参考组态相互作用(MRCI+Q)方法结合6-311++G(3df,3pd)基组计算了NaC分子基态(X4∑)以及三个低电子激发态(a2Π, b2∑, A4Π)的势能曲线(PECs), 确定出相应态的平衡键长Re和垂直激发能Te. 然后将PECs拟合到Murrel-Sorbie(MS)解析势能函数形式, 继而获得各态的光谱数据: 谐振频率ωe、离解能De、非谐性常数ωeΧe、转动常数Be、Drot和振转耦合常数αe. 计算结果表明: X4∑、a2Π、b2∑是三个束缚电子态. 基态X4∑的平衡键长为0.2259 nm, 谐振频率为431 cm-1, 离解能为1.92 eV, 目前计算值与实验结果和其它理论值一致. a2Π和b2∑激发态的核间距、谐振频率分别为0.2447、0.2369 nm 和329、335 cm-1, Te分别为1.58 和1.75eV, De则为0.71和0.42 eV. A4Π态为排斥态, 其相对基态的垂直激发能为2.48 eV. 通过求解核运动的薛定谔方程找到了转动量子数J=0时NaC分子三个低电子态(X4∑, a2Π, b2∑)的全部振动能级和转动惯量.

Ground and Low-Lying Excited States of NaC Molecule

Potential energy curves (PECs) for the ground electronic state (X~4∑) and the three lowest excited electronic states (a~2∏, b~2∑, A~4∏) of NaC molecule were calculated using the multi-configuration reference single and double excited configuration interaction method, including Davidson's corrections for quadruple excitations (MRCI+Q). The equilibrium bond length R_e and the vertical excited energy T_e were determined directly and the PECs were fitted to an analytical Murrell-Sorbie (MS) potential function to determine the spectroscopic parameters, which were the rotation coupling constant ω_e, dissociation energy D_e, the anharmonic constant ω_eX_e, the equilibrium rotation constant B_e and D_(rot), and the vibration-rotation coupling constant а_e. These values were also compared and were in agreement with other theoretical and experimental results currently available. It is evident that the X~4∑, a~2∏, and b~2∑ states are bound. We found that in the ground state X~4∑, R_e was 0.2259 nm, ω_e was 431 cm~(-1), and D_e was 1.92 eV, while in the excited states a~2∏ and b~2∑, R_e and ω_e were 0.2447, 0.2369 nm and 329, 335 cm~(-1), respectively. T_e was found to be 1.58 and 1.75 eV and D_e was 0.71 and 0.42 eV. A~4∏ is a repulsive excited state when T_e is 2.48 eV relative to the ground state. By solving the radial Schr(o)dinger equation of nuclear motion the vibration levels and inertial rotation constant at rotational quantum number J=0 are reported for the X~4, a~2∏, and b~2∑ states.