期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 116, 期 5, 页码 1344-1352出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp211220v
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资金
- National Science Foundation [CHE-0911225]
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [0911225] Funding Source: National Science Foundation
The electronic spectrum of Ni+(H2O) has been measured from 16200 to 18000 cm(-1) using photofragment spectroscopy. Transitions to two excited electronic states are observed; they are sufficiently long-lived that the spectrum is vibrationally and partially rotationally resolved. An extended progression in the metal ligand stretch is observed, and the absolute vibrational quantum numbering is assigned by comparing isotopic shifts between Ni-58(+)(H2O) and Ni-60(+)(H2O). Time-dependent density functional calculations aid in assigning the spectrum. Two electronic transitions are observed, from the (2)A(1) ground state (which correlates to the D-2, (3)d(9) ground state of Ni+) to the 3(2)A(1) and 2(2)A(2) excited states. These states are nearly degenerate and correlate to the F-2, 3d(8)4s excited state of Ni+. Both transitions are quite weak, but surprisingly, the transition to the (2)A(2) state is stronger, although it is symmetry-forbidden. The 3d(8)4s states of Ni+ interact less strongly with water than does the ground state; therefore, the excited states observed are less tightly bound and have a longer metal ligand bond than the ground state. Calculations at the CCSD(T)/aug-cc-pVTZ level predict that binding to Ni+ increases the H-O-H angle in water from 104.2 to 107.5 degrees as the metal removes electron density from the oxygen lone pairs. The photodissociation spectrum shows well-resolved rotational structure due to rotation about the Ni-O axis. This permits determination of the spin rotation constants epsilon(alpha alpha)'' = 12 cm(-1) and epsilon(alpha alpha)' = 3 cm(-1) and the excited state rotational constant A' = 14.5 cm(-1). This implies a H-O-H angle of 104 +/- 1 degrees in the 2(2)A(2) excited state. The O-H stretching frequencies of the ground state of Ni+(H2O) were measured by combining IR excitation with visible photodissociation in a double resonance experiment. The O-H symmetric stretch is nu(1)'' = 3616.5 cm(-1); the antisymmetric stretch is nu(s)'' = 3688 cm(-1). These values are 40 and 68 cm(-1) lower, respectively, than those in bare H2O.
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