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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >X-tilde ~3B_1, a-tilde ~1A_1, b-tilde ~1B_1, and c-tilde 1~∑_g~+ Electronic States of NH_2~+
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X-tilde ~3B_1, a-tilde ~1A_1, b-tilde ~1B_1, and c-tilde 1~∑_g~+ Electronic States of NH_2~+

机译：X波浪线〜3B_1，a波浪线〜1A_1，b波浪线〜1B_1和c波浪线1〜∑_g〜+ NH_2〜+的电子态

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摘要

Ab initio molecular electronic structure theory has been employed in order to investigate systematically the X-tilde ~3B_1, a-tilde ~1A_1, b-tilde ~1B_1, and c-tilde 1~∑_g~+ states of NH_2~+, with emphasis placed on the b-tilde ~1B_1 and c-tilde 1~250L芲g~+ states. The self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), complete active space (CAS) SCF, and CASSCF second-order configuration interaction (SOCI) wave functions with nine basis sets, the largest being a triple-ξ basis set with three sets of polarization functions and two additional sets of higher angular momentum and diffuse functions [TZ3P(2f, 2d) + 2diff], were used to determine equilibrium geometries, harmonic vibrational frequencies, infrared (IR) intensities, and dipole moments. The ground, first, and second excited states are confirmed to be bent, while the third excited state is predicted to be linear. The bond angles of NH_2~+ are shown to be larger than those of the corresponding isoelectronic CH_2 molecule. At the highest level of theory, TZ3P(2f, 2d) + 2diff CASSCF-SOCI, the triplet-singlet splitting is predicted to be 29.4 kcal/mol (1.28 eV, 10 300 cm~(-1)), which is in good agreement with the experimental observation of 30.1 kcal/mol (1.305 eV, 10 530 cm~(-1)).With the same method, the second excited state (b-tilde ~1B_1) lies 43.7 kcal/mol (1.89 eV, 15 300 cm~(-1)) above the ground state, which is significantly lower than the experimentally proposed value of 2.54 eV. The third excited state (c-tilde 1~∑_g~+) is predicted to lie 77.0 kcal/mol (3.34 eV, 26 900 cm~(-1)) above the ground state. The equilibrium geometry of this c-tilde ~1∑_g~+ state is determined to be r_e = 1.030 A at the TCSCF-CISD level with the largest basis set. Since the IR intensities of all active vibrational modes are predicted to be substantial, IR spectroscopic studies of the four states are feasible. However, of the six fundamentals experimentally assigned to date, two appear to be incorrect. The energy separations among the four lowest-lying states of NH_2~+ are found to be larger than the corresponding states of CH_2.
机译：为了从系统角度研究NH_2〜+的X-tilde〜3B_1，a-tilde〜1A_1，b-tilde〜1B_1和c-tilde 1〜∑_g〜+状态，使用了从头算分子电子结构理论。重点放在b波浪线〜1B_1和c波浪线1〜250L花g〜+状态。自洽场（SCF），具有单激发和双激发的配置相互作用（CISD），完整活动空间（CAS）SCF和具有9个基集的CASSCF二阶配置相互作用（SOCI）波函数，最大的是具有三组极化函数和另外两组高角动量和扩散函数[TZ3P（2f，2d）+ 2diff]的三重ξ基集用于确定平衡几何，谐波振动频率，红外（IR）强度，和偶极矩。确认基态，第一和第二激发态已弯曲，而第三激发态被预测为线性。结果表明，NH_2〜+的键角大于相应的等电子CH_2分子的键角。在最高理论水平TZ3P（2f，2d）+ 2diff CASSCF-SOCI上，三重峰-单峰分裂预计为29.4 kcal / mol（1.28 eV，10 300 cm〜（-1）），表现良好与实验观察到的30.1 kcal / mol（1.305 eV，10 530 cm〜（-1））一致。第二种激发态（b-tilde〜1B_1）为4​​3.7 kcal / mol（1.89 eV，15）比基态高300 cm〜（-1）），大大低于实验提出的2.54 eV值。预计第三激发态（c-tilde 1〜∑_g〜+）高于基态77.0 kcal / mol（3.34 eV，26 900 cm〜（-1））。在具有最大基础集的TCSCF-CISD级别上，此c-tilde〜1∑_g〜+状态的平衡几何确定为r_e = 1.030A。由于预计所有活动振动模式的红外强度都很大，因此对四种状态的红外光谱研究是可行的。但是，到目前为止，在实验分配的六个基本原理中，有两个似乎不正确。发现NH_2〜+的四个最低处的能级之间的能量间隔大于CH_2的相应状态。

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