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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Dissociation energy and electronic and vibrational spectroscopy of Co~+(H_2O) and its isotopomers
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Dissociation energy and electronic and vibrational spectroscopy of Co~+(H_2O) and its isotopomers

机译：Co〜+（H_2O）及其异构体的解离能及电子和振动光谱

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摘要

The electronic spectra of Co~+(H_2O), Co~+(HOD), and Co~+(D_2O) have been measured from 13 500 to 18 400 cm~(-1) using photodissociation spectroscopy. Transitions to four excited electronic states with vibrational and partially resolved rotational structure are observed. Each electronic transition has an extended progression in the metal-ligand stretch, v_3, and the absolute vibrational quantum numbering is assigned by comparing isotopic shifts between Co~+(H_2 ~(16)O) and Co~+(H_2 ~(18)O). For the low-lying excited electronic states, the first observed transition is to v3′ = 1. This allows the Co~+-(H_2O) binding energy to be determined as D 0(0 K)(Co~+-H_2O) = 13730 ± 90 cm ~(-1) (164.2 ± 1.1 kJ/mol). The photodissociation spectrum shows a well-resolved Ka band structure due to rotation about the Co-O axis. This permits determination of the spin rotation constants ?μaa″ = -6 cm~(-1) and ?μaa′= 4 cm ~(-1). However, the Ka rotational structure depends on v 3′. These perturbations in the spectrum make the rotational constants unreliable. From the nuclear spin statistics of the rotational structure, the ground state is assigned as 3B1. The electronic transitions observed are from the Co~+(H_2O) ground state, which correlates to the cobalt ion's 3F, 3d8 ground state, to excited states which correlate to the ~3F, 3d~74s and ~3P, 3d~8 excited states of Co~+. These excited states of Co~+ interact less strongly with water than the ground state. As a result, the excited states are less tightly bound and have longer metal-ligand bonds. Calculations at the CCSD(T)/aug-cc-pVTZ level also predict that binding to Co~+ increases the H-O-H angle in water from 104.1 to 106.8, as the metal removes electron density from the oxygen lone pairs. The O-H stretching frequencies of the ground electronic state of Co~+(H_2O) and Co~+(HOD) have been measured by combining IR excitation with visible photodissociation in a double resonance experiment. In Co~+(H_2O) the O-H symmetric stretch is ν1″ = 3609.7 ± 1 cm~(-1). The antisymmetric stretch is ν5″ = 3679.5 ± 2 cm ~(-1). These values are 47 and 76 cm~(-1), respectively, lower than those in bare H_2O. In Co~+(HOD) the O-H stretch is observed at 3650 cm~(-1), a red shift of 57 cm~(-1) relative to bare HOD.
机译：使用光解离光谱法测量了Co〜+（H_2O），Co〜+（HOD）和Co〜+（D_2O）的电子光谱，范围为13500至18400 cm〜（-1）。观察到具有振动和部分分解的旋转结构的四个激发电子态的跃迁。每个电子跃迁在金属配体拉伸v_3中都有一个扩展级数，并且通过比较Co〜+（H_2〜（16）O）和Co〜+（H_2〜（18）之间的同位素位移来分配绝对振动量子编号O）。对于低层激发电子态，观察到的第一个跃迁为v3'=1。这使Co〜+-（H_2O）的结合能可以确定为D 0（0 K）（Co〜+ -H_2O）= 13730±90 cm〜（-1）（164.2±1.1 kJ /摩尔）。由于绕Co-O轴旋转，光解离光谱显示出良好分辨的Ka带结构。这允许确定自旋旋转常数Δμaa″ ＝-6cm-1（-1）和μμaa′＝ 4cm-1（-1）。然而，Ka旋转结构取决于v 3'。频谱中的这些扰动使旋转常数不可靠。根据旋转结构的核自旋统计，将基态指定为3B1。观察到的电子跃迁是从与钴离子的3F，3d8基态相关的Co〜+（H_2O）基态到与〜3F，3d〜74s和〜3P，3d〜8激发态​​相关的激发态Co〜+。 Co〜+的这些激发态与水的相互作用不如基态强。结果，激发态的键合紧密度较低，并且具有更长的金属-配体键。在CCSD（T）/ aug-cc-pVTZ水平进行的计算还预测，与Co〜+的结合会使水中的H-O-H角从104.1增加到106.8，因为金属会从孤氧对中除去电子密度。在双共振实验中，结合红外激发和可见光离解，测量了Co〜+（H_2O）和Co〜+（HOD）基态电子的O-H拉伸频率。在Co〜+（H_2O）中，O-H对称拉伸为ν1“ = 3609.7±1 cm〜（-1）。反对称拉伸为ν5''= 3679.5±2 cm〜（-1）。这些值分别比裸露的H_2O低47和76 cm〜（-1）。在Co〜+（HOD）中，在3650 cm〜（-1）处观察到O-H拉伸，相对于裸HOD，红色偏移为57 cm〜（-1）。

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