Multidimensional quantum dynamics and infrared spectroscopy of hydrogen bonds

The laser fluorescence excitation spectra and single vibronic level fluorescence spectra have been measured for jet‐cooled tropolone (–OH) and tropolone (–OD). The ν’11(a1), ν12(a1), and ν’19(a2), modes have been newly identified in the excitation spectrum of tropolone (–OH), in addition to the previously observed ν13(a1), ν’14(a1), ν25(b1), and ν’26(b1) modes. The tunneling doublet splittings of these modes in the A 1B2 state have been determined to investigate the effect of the vibrational excitation on the proton tunneling dynamics. The tunneling splitting is highly mode specific. The ν13(a1) and ν’14(a1) skeletal deformation modes are strongly coupled to the proton transfer coordinate and enhance tunneling, whereas the ν19(a2) skeletal twisting mode as well as ν’25(b1) and ν26(b1) out‐of‐plane bending modes diminish tunneling. The ν’11(a1) C–C stretching and ν12(a1) C–C–C bending modes are considered to be weakly coupled to the proton transfer coordinate, because the tunneling splittings of these mod...

Electronic spectra of jet-cooled tropolone. Effect of the vibrational excitation on the proton tunneling dynamics

Quantum dynamics in low-temperature chemistry

Tunneling energy splittings of vibrationally excited states are calculated quantum mechanically using several models of two‐dimensional symmetric double well potentials. Various effects of vibrational excitation on tunneling are found to appear, depending on the topography of potential energy surface; the symmetry of the mode coupling plays an essential role. Especially, oscillation of tunneling splitting with respect to vibrational quantum number can occur and is interpreted by a clear physical picture based on the semiclassical theory formulated recently [Takada and Nakamura, J. Chem. Phys. 100, 98 (1994)]. The mixed tunneling in the C region found there allows the wave functions to have nodal lines in classically inaccessible region and can cause the suppression of the tunneling. The above analysis is followed by the interpretation of recent experiments of proton tunneling in tropolone. Ab initio molecular orbital calculations are carried out for the electronically ground state. A simple three‐dimensio...

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Effects of vibrational excitation on multidimensional tunneling: General study and proton tunneling in tropolone

The excited-state double-proton transfer (ESDPT) reaction in the dual hydrogen-bonded 7-azaindole dimer (7AI 2 ) in a supersonic jet expansion has been extensively studied with various laser spectroscopic methods and quantum chemistry calculations by many groups. This article reviews the results and discussions associated with stepwise and concerted mechanism controversy on ESDPT of 7AI 2 together with the excited-state dynamics associated with ESDPT.

Excited-state double-proton transfer in a model DNA base pair : Resolution for stepwise and concerted mechanism controversy in the 7-azaindole dimer revealed by frequency- and time-resolved spectroscopy

Vibrational mode-specific tunneling splittings in the Ã states of deuterated tropolones

The laser fluorescence excitation spectrum and the single vibronic level fluorescence spectra from the \ ildeA1B2 state of tropolone have been measured in a supersonic free jet. Some vibronic bands observed in the region of 270–450 cm−1 from the 000 band have been assigned. A tunneling doublet separation for the ν′14 in-plane ring deformation mode has been measured to be 30 cm−1, which is significantly larger than 19 cm−1 for that for the zero-point level, suggesting that the average geometry of the ν′14 mode deviates significantly from that of the zero-point level.

The Electronic Spectra of Jet-Cooled Tropolone. Vibrational Assignment for the \ildeA1B2–\ildeX1A1 Transition

Electronic spectra of jet-cooled tropolone(-OD). vibrational analysis for the Ã 1B2-X̃ 1A1 transition

The laser fluorescence excitation spectrum of jet-cooled tropolone-3-d has been measured to investigate the effect of an unsymmetrical substitution of a deuterium on proton tunneling and the equilibrium geometry.

Yusuke Nagashima

Papers

Electronic spectra of jet-cooled tropolone. Effect of the vibrational excitation on the proton tunneling dynamics

Vibrational mode-specific tunneling splittings in the Ã states of deuterated tropolones

The Electronic Spectra of Jet-Cooled Tropolone. Vibrational Assignment for the \ildeA1B2–\ildeX1A1 Transition

Electronic spectra of jet-cooled tropolone(-OD). vibrational analysis for the Ã 1B2-X̃ 1A1 transition

Electronic spectrum of jet-cooled tropolone-3-d.