SiH自由基分子激发态的多参考组态相互作用计算简

运用含Davidson修正的多参考组态相互作用(MRCI+Q)方法,在def2-qzvpp基组水平上对SiH自由基分子对应最低三个离解限Si(3 P,1 D,1 S)+H(2 S)的共6个双重态X2Π,A2Δ,B2∑-,C2∑+,D2∑+,F2Π和2个四重态a4∑-,b4 P在0.1nm~0.6nm范围内进行了势能扫描计算.得出X2Π,A2Δ和a4∑-态为典型的束缚态,其离解能分别为3.17eV,0.96eV和1.49eV,平衡核间距分别为0.1523nm,0.1533nm和0.1499nm.其中B2∑-态在接近基态平衡核间距处与A2Δ态极为靠近,且在R=0.1764nm与A2Δ态发生交叉,导致SiH最主要的电子激发跃迁A2Δ-X2Π中仅主要观测到(0-0)带,这与实验结果完全一致.C2∑+和D2∑+态在R=0.1799nm处发生由于对称性相同而出现回避交叉.对于束缚态X2Π,A2Δ,D2∑+和a4∑-,数值求解核运动的径向Schrdinger方程预测出各电子态所有可能的振动能级和转动常数,进而拟合得到的光谱常数与已有的实验数据符合较好.

MRCI calculations for the excited states of SiH molecule

The potential energy curves (PECs) of SiH correlating to the lowest three dissociation limits Si(3P, 1D, 1S)+H(2S) are constructed by using multi-reference configuration interaction including Davidson correction (MRCI+Q) approach with the basis set of def2-qzvpp. Totally PECs for the six doublet states (X2, A2, B2, C2, D2, F2and two quartet states (a4b4 are scanned with the internuclear distance range from 0.1 to 0.6nm, and the results show that X2A2 and a4are the typical bound states with dissociation energies of 3.17eV, 0.96eV, and 1.49eV, and equilibrium nuclear distances of 0.1523nm, 0.1533nm, and 0.1499nm, respectively. The PEC of the repulsive state B2 is cross with A2state at R=0.1764nm which is near the equilibrium distance of the A state, this is completely consistent with the experimental results that only the band was observed in the emission spectrum of A2X2transition. The C2 and D2states occur the avoiding cross at R=nm due to the same symmetry. With the potentials, all of the vibrational levels and inertial rotation constants pertaining to the bound states X2A2D2and a4 are predicted by numerically solving the radial Schrödinger equation of nuclear motion. Then the obtained spectroscopic data are all found to agree well with the experiment.