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Semenov A. Mixed quantum/classical theory for rotationally and vibrationally inelastic scattering of open-shell molecules and its application to the NH(X 3Σ −) + He collisional system. J Chem Phys 2018; 148:244305. [DOI: 10.1063/1.5037164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alexander Semenov
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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Semenov A, Babikov D. MQCT. I. Inelastic Scattering of Two Asymmetric-Top Rotors with Application to H 2O + H 2O. J Phys Chem A 2017; 121:4855-4867. [PMID: 28581295 DOI: 10.1021/acs.jpca.7b03554] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A mixed quantum/classical theory (MQCT) for the inelastic collision of two asymmetric-top rotor molecules is developed. In this method, the quantum state-to-state transitions between the rotational states of molecules (internal) are treated quantum mechanically using the time-dependent Schrodinger equation, whereas their relative translational motion (responsible for scattering) is treated classically, using the average trajectory approach. Two versions of the formula for transition matrix elements are presented: a straightforward approach that uses numerical multidimensional quadrature over all the internal degrees of freedom and a more standard analytic approach that uses the expansion of the PES over the basis set of spherical harmonics. Adaptation to the case of identical molecules scattering is presented and is applied to the rotational excitation of two water molecules, H2O + H2O, using the PES from recent literature. Calculations of collisional excitation from the ground state of the system into a number of low-lying excited rotational states are carried out in a broad range of energies. Analysis of computed opacity functions shows a rather unusual scattering regime, dominated by a strong anisotropic long-range interaction (dipole-dipole). The coupled-states (CS) approximation is tested and found to agree semiquantitatively (within a factor of 2) with the fully coupled version of the method. Differential cross sections for the elastic scattering indicate a very narrow forward scattering peak.
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Affiliation(s)
- Alexander Semenov
- Chemistry Department, Wehr Chemistry Building, Marquette University , Milwaukee, Wisconsin 53201-1881, United States
| | - Dmitri Babikov
- Chemistry Department, Wehr Chemistry Building, Marquette University , Milwaukee, Wisconsin 53201-1881, United States
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Sánchez EQ, Dubernet ML. Theoretical study of HCN-water interaction: five dimensional potential energy surfaces. Phys Chem Chem Phys 2017; 19:6849-6860. [PMID: 28218316 DOI: 10.1039/c6cp07894j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new five-dimensional potential energy surface is calculated at the coupled-cluster CCSD(T) level of theory for the HCN-water system, treating both monomers as rigid rotors. The associated methodology, which combines extensive ab initio calculations of moderate accuracy (CCSD(T)/AVDZ) and a fitting procedure involving a much lower angular coverage with more accurate ab initio calculations (CCSD(T)/CBS), is described in detail. This methodology provides a time-saving approach to compute quantitatively accurate potential energy surfaces with reasonable computational effort. Our potential reproduces the main features reported in the literature, and will allow us to perform the first quantum and semi-classical simulations of the collisional dynamic on this system.
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Affiliation(s)
- Ernesto Quintas Sánchez
- LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne University, UPMC Univ Paris 06, 5 Place Janssen, 92190 Meudon, France.
| | - Marie-Lise Dubernet
- LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne University, UPMC Univ Paris 06, 5 Place Janssen, 92190 Meudon, France.
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Sarma G, Saha AK, Bishwakarma CK, Scheidsbach R, Yang CH, Parker D, Wiesenfeld L, Buck U, Mavridis L, Marinakis S. Collision energy dependence of state-to-state differential cross sections for rotationally inelastic scattering of H 2O by He. Phys Chem Chem Phys 2017; 19:4678-4687. [PMID: 28127600 DOI: 10.1039/c6cp06495g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The inelastic scattering of H2O by He as a function of collision energy in the range 381 cm-1 to 763 cm-1 at an energy interval of approximately 100 cm-1 has been investigated in a crossed beam experiment using velocity map imaging. Change in collision energy was achieved by varying the collision angle between the H2O and He beam. We measured the state-to-state differential cross section (DCS) of scattered H2O products for the final rotational states JKaKc = 110, 111, 221 and 414. Rotational excitation of H2O is probed by (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectroscopy. DCS measurements over a wide range of collision energies allowed us to probe the H2O-He potential energy surface (PES) with greater detail than in previous work. We found that a classical approximation of rotational rainbows can predict the collision energy dependence of the DCS. Close-coupling quantum mechanical calculations were used to produce DCS and partial cross sections. The forward-backward ratio (FBR), is introduced here to compare the experimental and theoretical DCS. Both theory and experiments suggest that an increase in the collision energy is accompanied with more forward scattering.
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Affiliation(s)
- Gautam Sarma
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | - Ashim Kumar Saha
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | | | - Roy Scheidsbach
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | - Chung-Hsin Yang
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
| | - David Parker
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | | | - Udo Buck
- Max-Planck-Institut für Dynamik und Selbst-Organisation, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Lazaros Mavridis
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, Joseph Priestley Building, Mile End Road, London, E1 4NS, UK.
| | - Sarantos Marinakis
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, Joseph Priestley Building, Mile End Road, London, E1 4NS, UK.
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Semenov A, Babikov D. Inelastic Scattering of Identical Molecules within Framework of the Mixed Quantum/Classical Theory: Application to Rotational Excitations in H2 + H2. J Phys Chem A 2016; 120:3861-6. [PMID: 27187769 DOI: 10.1021/acs.jpca.6b04556] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Theoretical foundation is laid out for description of permutation symmetry in the inelastic scattering processes that involve collisions of two identical molecules, within the framework of the mixed quantum/classical theory (MQCT). In this approach, the rotational (and vibrational) states of two molecules are treated quantum-mechanically, whereas their translational motion (responsible for scattering) is treated classically. This theory is applied to H2 + H2 system, and the state-to-state transition cross sections are compared versus those obtained from the full-quantum calculations and experimental results from the literature. Good agreement is found in all cases. It is also found that results of MQCT, where the Coriolis coupling is included classically, are somewhat closer to exact full-quantum results than results of the other approximate quantum methods, where those coupling terms are neglected. These new developments allow applications of MQCT to a broad variety of molecular systems and processes.
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Affiliation(s)
- Alexander Semenov
- Chemistry Department, Wehr Chemistry Building, Marquette University , Milwaukee, Wisconsin 53201-1881, United States
| | - Dmitri Babikov
- Chemistry Department, Wehr Chemistry Building, Marquette University , Milwaukee, Wisconsin 53201-1881, United States
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Babikov D, Semenov A. Recent Advances in Development and Applications of the Mixed Quantum/Classical Theory for Inelastic Scattering. J Phys Chem A 2015; 120:319-31. [DOI: 10.1021/acs.jpca.5b09569] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dmitri Babikov
- Chemistry
Department, Wehr
Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Alexander Semenov
- Chemistry
Department, Wehr
Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
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Semenov A, Babikov D. Mixed Quantum/Classical Theory for Molecule–Molecule Inelastic Scattering: Derivations of Equations and Application to N2 + H2 System. J Phys Chem A 2015; 119:12329-38. [DOI: 10.1021/acs.jpca.5b06812] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Alexander Semenov
- Chemistry
Department, Wehr Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Dmitri Babikov
- Chemistry
Department, Wehr Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
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Semenov A, Dubernet ML, Babikov D. Mixed quantum/classical theory for inelastic scattering of asymmetric-top-rotor + atom in the body-fixed reference frame and application to the H₂O + He system. J Chem Phys 2014; 141:114304. [PMID: 25240355 DOI: 10.1063/1.4895607] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The mixed quantum/classical theory (MQCT) for inelastic molecule-atom scattering developed recently [A. Semenov and D. Babikov, J. Chem. Phys. 139, 174108 (2013)] is extended to treat a general case of an asymmetric-top-rotor molecule in the body-fixed reference frame. This complements a similar theory formulated in the space-fixed reference-frame [M. Ivanov, M.-L. Dubernet, and D. Babikov, J. Chem. Phys. 140, 134301 (2014)]. Here, the goal was to develop an approximate computationally affordable treatment of the rotationally inelastic scattering and apply it to H2O + He. We found that MQCT is somewhat less accurate at lower scattering energies. For example, below E = 1000 cm(-1) the typical errors in the values of inelastic scattering cross sections are on the order of 10%. However, at higher scattering energies MQCT method appears to be rather accurate. Thus, at scattering energies above 2000 cm(-1) the errors are consistently in the range of 1%-2%, which is basically our convergence criterion with respect to the number of trajectories. At these conditions our MQCT method remains computationally affordable. We found that computational cost of the fully-coupled MQCT calculations scales as n(2), where n is the number of channels. This is more favorable than the full-quantum inelastic scattering calculations that scale as n(3). Our conclusion is that for complex systems (heavy collision partners with many internal states) and at higher scattering energies MQCT may offer significant computational advantages.
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Affiliation(s)
- Alexander Semenov
- Chemistry Department, Wehr Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, USA
| | - Marie-Lise Dubernet
- PSL Research University, Observatoire de Paris, Sorbonne Universités, UPMC Univ Paris 06, ENS, UCP, CNRS, UMR8112, LERMA, 5 Place Janssen, 92195 Meudon, France
| | - Dmitri Babikov
- Chemistry Department, Wehr Chemistry Building, Marquette University, Milwaukee, Wisconsin 53201-1881, USA
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