Rovibrational Parameters for cis-Nitrous Acid

Guilmot, Jean Michel; Godefroid, Michel; Herman, Michel

doi:10.1006/jmsp.1993.1187

Cited by 50 publications

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“…Presumably, the coupling is mediated by the matrix, as this reaction has not been reported in the gas-phase so far [8]. The molecule is extremely well characterized by vibrational and electronic spectroscopy [8][9][10][11][12][13][14][15][16][17][18]. Furthermore, because of its small size, the molecule is particularly suited for theoretical studies on the absolutely highest conceivable level [19][20][21][22], and therefore has prototype character.…”

Section: Introductionmentioning

confidence: 99%

The infrared-driven cis–trans isomerization of nitrous acid HONO III: A mixed quantum–classical simulation

Hamm

2008

Chemical Physics

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The infrared-driven cis-trans isomerization of nitrous acid HONO III: a mixed quantum-classical simulationHamm, P Hamm, P (2008 The infrared-driven cis-trans isomerization of nitrous acid HONO III: a mixed quantum-classical simulation Abstract A mixed quantum-classical simulation of the IR-driven cis-trans isomerization of HONO in a Kr matrix at 30 K is presented, treating the hydrogen atom as quantum particle and the Kr matrix as well as intermolecular degrees of freedom of the ONO-body as classical. A new method is presented to time-propagate the coupled set of equations in a DVR basis in internal spherical coordinates, rather than in laboratory frame fixed cartesian coordinates. In spherical coordinates, a much more precise computation of the weak vibrational couplings is possible using a still manageable basis size. Good qualitative agreement between simulation and experiment is obtained, underestimating relaxation and isomerization rates by a modest factor approximate to 5. Upon matrix fluctuations, frequent curve crossings occur between the initially excited OH-stretch vibration and a closely lying combination mode of torsional and bending coordinate that lead to a transfer of population. The subsequent pathway of energy flow is deduced and discussed within a tier model, where trans-states, that belong to the second tier, are populated through a first tier of states that is composed of combinations of bending and torsional excitations. No specific energy pathway is revealed that would funnel the hydrogen atom directly towards the trans-side, hence the experimentally observed high cis -> trans quantum yield of close to one probably has to be explained in a statistical scenario on a timescale much longer than that of the present simulation. (C) 2007 Elsevier B.V. All rights reserved. The infrared-driven cis-trans isomerization of nitrous acid HONO III: A mixed quantum-classical simulationPeter Hamm Universität Zürich, Winterthurerstr. 190, Switzerland (Dated: December 1, 2008)A mixed quantum-classical simulation of the IR driven cis-trans isomerization of HONO in a Kr matrix at 30 K is presented, treating the hydrogen atom as quantum particle and the Kr matrix as well as intermolecular degrees of freedom of the ONO-body as classical. A new method is presented to time-propagate the coupled set of equations in a DVR basis in internal spherical coordinates, rather than in laboratory frame fixed cartesian coordinates. In spherical coordinates, a much more precise computation of the weak vibrational couplings is possible using a still manageable basis size. Good qualitative agreement between simulation and experiment is obtained, underestimating relaxation and isomerization rates by a modest factor ≈ 5. Upon matrix fluctuations, frequent curve crossings occur between the initially excited OH stretch vibration and a closely lying combination mode of torsional and bending coordinate that lead to a transfer of population. The subsequent pathway of energy flow is deduced and discussed within a tier model, where t...

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Section: Introductionmentioning

confidence: 99%

The infrared-driven cis–trans isomerization of nitrous acid HONO III: A mixed quantum–classical simulation

Hamm

2008

Chemical Physics

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“…7. Where experimental gas-phase values are available, 31,32 we find small deviations on the order of a few wavenumbers, hinting to a matrix effect for these anharmonicities ͑just like the vibrational frequencies shift a bit in the matrix͒.…”

Section: Discussionmentioning

confidence: 71%

“…Furthermore we observed that cooling of trans-HONO proceeds through the overtones of one particular mode. Based on the number of quanta we observed and the anharmonic coupling constants available in literature, 7,31,32 we suggested that the "cooling mode" is the ONO bend vibration. This is not the lowest energy mode of the trans isomer but lies Ϸ60 cm −1 above the OH-torsional mode ͑see Table I for the normal mode frequencies of HONO in solid Kr͒.…”

Section: Introductionmentioning

confidence: 76%

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Intramolecular vibrational energy relaxation in nitrous acid (HONO)

Botan

Hamm

2008

The Journal of Chemical Physics

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Intramolecular vibrational energy relaxation (IVR) in nitrous acid (HONO) is studied with the help of ultrafast two-color pump-probe spectroscopy. In a previous paper [V. Botan et al., J. Chem. Phys. 124, 234511 (2006)], it has been observed that trans-HONO cools through a cascade of overtones of one specific mode after pumping the OH stretch vibration. We had suggested that this cooling mode is the ONO bend vibration. Furthermore, molecules that have initially been excited by the OH stretch vibration of cis-HONO and then underwent isomerization follow the same relaxation pathway. In the present study, we extend the investigation of IVR of cis-and trans-HONO to the N=O stretch and HON bend spectral regions, finding further evidence that the bottleneck of trans cooling is indeed the ONO bend vibration. In combination with information on the anharmonic coupling constants of different modes, the energy relaxation dynamics preceding this cooling cascade can also be followed in unprecedented detail. Intramolecular vibrational energy relaxation ͑IVR͒ in nitrous acid ͑HONO͒ is studied with the help of ultrafast two-color pump-probe spectroscopy. In a previous paper ͓V. Botan et al., J. Chem. Phys. 124, 234511 ͑2006͔͒, it has been observed that trans-HONO cools through a cascade of overtones of one specific mode after pumping the OH stretch vibration. We had suggested that this cooling mode is the ONO bend vibration. Furthermore, molecules that have initially been excited by the OH stretch vibration of cis-HONO and then underwent isomerization follow the same relaxation pathway. In the present study, we extend the investigation of IVR of cis-and trans-HONO to the N = O stretch and HON bend spectral regions, finding further evidence that the bottleneck of trans cooling is indeed the ONO bend vibration. In combination with information on the anharmonic coupling constants of different modes, the energy relaxation dynamics preceding this cooling cascade can also be followed in unprecedented detail. Intramolecular vibrational energy relaxation in nitrous acid "HONO…

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“…We chose the PES¯t with 90 neurons for use in the MCTDH calculations of the vibrational state frequencies. The fundamental vibrational modes for the lowest energy trans-HONO isomer determined based on the NN-expnn¯ts (with 90 neurons) to the CCSD(T)-F12/ccpVTZ-F12 and CCSD(T)/CBS ab initio data are provided in Table 6 along with a comparison to previously measured experimental results [108][109][110][111][112][113] and recent previous theoretical results using MCTDH. 114 The absolute di®erences as compared to the experiment range from 1.1 cm À1 to 16.8 cm À1 on the CCSD(T)-F12 PES (0.3-12.9 cm À1 on the CCSD(T)/CBS PES) and the RMSE is 9.5 cm À1 (7.0 for CBS PES) for the trans-HONO isomer.…”

Section: Honomentioning

confidence: 99%

Fitting potential energy surfaces to sum-of-products form with neural networks using exponential neurons

Brown

Pradhan

2017

J. Theor. Comput. Chem.

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In this paper, the use of the neural network (NN) method with exponential neurons for directlȳ tting ab initio data to generate potential energy surfaces (PESs) in sum-of-product form will be discussed. The utility of the approach will be highlighted using¯ts of CS 2 , HFCO, and HONO ground state PESs based upon high-level ab initio data. Using a generic interface between the neural network PES¯tting, which is performed in MATLAB, and the Heidelberg multi-conguration time-dependent Hartree (MCTDH) software package, the PESs have been tested via comparison of vibrational energies to experimental measurements. The review demonstrates the potential of the PES¯tting method, combined with MCTDH, to tackle high-dimensional quantum dynamics problems.

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Rovibrational Parameters for cis-Nitrous Acid

Cited by 50 publications

References 0 publications

The infrared-driven cis–trans isomerization of nitrous acid HONO III: A mixed quantum–classical simulation

The infrared-driven cis–trans isomerization of nitrous acid HONO III: A mixed quantum–classical simulation

Intramolecular vibrational energy relaxation in nitrous acid (HONO)

Fitting potential energy surfaces to sum-of-products form with neural networks using exponential neurons

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