1
|
Brooke JSA, Bernath PF, Western CM. Note: Improved line strengths of rovibrational and rotational transitions within the X3Σ− ground state of NH. J Chem Phys 2015; 143:026101. [DOI: 10.1063/1.4923422] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Affiliation(s)
- James S. A. Brooke
- Department of Chemistry, University of York, York YO10 5DD, United Kingdom
| | - Peter F. Bernath
- Department of Chemistry, University of York, York YO10 5DD, United Kingdom
- Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, Virginia 23529-0126, USA
| | - Colin M. Western
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| |
Collapse
|
2
|
Koput J. Ab initio ground-state potential energy function and vibration-rotation energy levels of imidogen, NH. J Comput Chem 2015; 36:1286-94. [PMID: 25920622 DOI: 10.1002/jcc.23931] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/07/2015] [Accepted: 04/10/2015] [Indexed: 12/18/2022]
Abstract
The accurate ground-state potential energy function of imidogen, NH, has been determined from ab initio calculations using the multireference averaged coupled-pair functional (MR-ACPF) method in conjunction with the correlation-consistent core-valence basis sets up to octuple-zeta quality. The importance of several effects, including electron correlation beyond the MR-ACPF level of approximation, the scalar relativistic, adiabatic, and nonadiabatic corrections were discussed. Along with the large one-particle basis set, all of these effects were found to be crucial to attain "spectroscopic" accuracy of the theoretical predictions of vibration-rotation energy levels of NH.
Collapse
Affiliation(s)
- Jacek Koput
- Department of Chemistry, Adam Mickiewicz University, 61-614, Poznań, Poland
| |
Collapse
|
3
|
Brooke JSA, Bernath PF, Western CM, van Hemert MC, Groenenboom GC. Line strengths of rovibrational and rotational transitions within the X3Σ− ground state of NH. J Chem Phys 2014; 141:054310. [DOI: 10.1063/1.4891468] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
4
|
Monge-Palacios M, Rangel C, Espinosa-Garcia J. Ab initio based potential energy surface and kinetics study of the OH + NH3 hydrogen abstraction reaction. J Chem Phys 2013; 138:084305. [PMID: 23464149 DOI: 10.1063/1.4792719] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A full-dimensional analytical potential energy surface (PES) for the OH + NH3 → H2O + NH2 gas-phase reaction was developed based exclusively on high-level ab initio calculations. This reaction presents a very complicated shape with wells along the reaction path. Using a wide spectrum of properties of the reactive system (equilibrium geometries, vibrational frequencies, and relative energies of the stationary points, topology of the reaction path, and points on the reaction swath) as reference, the resulting analytical PES reproduces reasonably well the input ab initio information obtained at the coupled-cluster single double triple (CCSD(T)) = FULL/aug-cc-pVTZ//CCSD(T) = FC/cc-pVTZ single point level, which represents a severe test of the new surface. As a first application, on this analytical PES we perform an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range, 200-2000 K. The forward rate constants reproduce the experimental measurements, while the reverse ones are slightly underestimated. However, the detailed analysis of the experimental equilibrium constants (from which the reverse rate constants are obtained) permits us to conclude that the experimental reverse rate constants must be re-evaluated. Another severe test of the new surface is the analysis of the kinetic isotope effects (KIEs), which were not included in the fitting procedure. The KIEs reproduce the values obtained from ab initio calculations in the common temperature range, although unfortunately no experimental information is available for comparison.
Collapse
Affiliation(s)
- M Monge-Palacios
- Departamento de Química Física, Universidad de Extremadura, 06071 Badajoz, Spain
| | | | | |
Collapse
|
5
|
Monge-Palacios M, Yang M, Espinosa-García J. QCT and QM calculations of the Cl(2P) + NH3 reaction: influence of the reactant well on the dynamics. Phys Chem Chem Phys 2012; 14:4824-34. [PMID: 22388701 DOI: 10.1039/c2cp00008c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A detailed dynamics study, using both quasi-classical trajectory (QCT) and reduced-dimensional quantum mechanical (QM) calculations, was carried out to understand the reactivity and mechanism of the Cl((2)P) + NH(3)→ HCl + NH(2) gas-phase reaction, which evolves through deep wells in the entry and exit channels. The calculations were performed on an analytical potential energy surface recently developed by our group, PES-2010 [M. Monge-Palacios, C. Rangel, J. C. Corchado and J. Espinosa-Garcia, Int. J. Quantum. Chem., 2011], together with a simplified model surface, mod-PES, in which the reactant well is removed to analyze its influence. The main finding was that the QCT and QM methods show a change of the reaction probability with collision energy, suggesting a change of the atomic-level mechanism of reaction with energy. This change disappeared when the mod-PES was used, showing that the behaviour at low energies is a direct consequence of the existence of the reactant well. Analysis of the trajectories showed that different mechanisms operate depending on the collision energy. Thus, while at high energies (E(coll) > 5 kcal mol(-1)) practically all trajectories are direct, at low energies (E(coll) < 3 kcal mol(-1)) the trajectories are indirect, i.e., with the mediation of a trapping complex in the entry and/or the exit wells. The reactant complex allows repeated encounters between the reactants, increasing the reaction probability at low energies. The differential cross section results reinforce this change of mechanism, showing also the influence of the reactant well on this reaction. Thus, the PES-2010 surface yields a forward-backward symmetry in the scattering, while when the reactant well is removed with the mod-PES the shape is more isotropic.
Collapse
Affiliation(s)
- M Monge-Palacios
- Departamento de Química Física, Universidad de Extremadura, 06071 Badajoz, Spain
| | | | | |
Collapse
|
6
|
Monge-Palacios M, Espinosa-Garcia J. Reaction-path dynamics calculations of the Cl + NH(3) hydrogen abstraction reaction: the role of the intermediate complexes. J Phys Chem A 2010; 114:4418-26. [PMID: 20205436 DOI: 10.1021/jp911664t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using ab initio information at the CCSD(T)/cc-pVTZ level, the reaction path for the Cl + NH(3) hydrogen abstraction reaction was traced, and the coupling terms between the reaction coordinate and the normal modes were analyzed along it. Two intermediate complexes were located in the entry channel and characterized close to the reactants. One of them presents a typical Cl...H-N bond, while the second presents a two-center/three-electron Cl[symbol:see text]N bond. Both complexes are on the reaction path and contribute to the final rate constants. With this information, the rate constants were calculated over the temperature range 200-2000 K, using variational transition state theory with multidimensional tunneling contributions, and were found to reproduce the experimental evidence in the common temperature range. Finally, analysis of the coupling terms showed qualitatively that vibrational excitation of the N-H stretch and the bending and umbrella modes in the reactant NH(3) enhances the forward thermal rate constants, and that, in the products, the H-Cl stretch mode and the bending mode in NH(2) could appear vibrationally excited, although the randomization of the energy in the well in the exit channel might diminish this excitation.
Collapse
Affiliation(s)
- M Monge-Palacios
- Departamento de Química Física, Universidad de Extremadura, 06071 Badajoz, Spain
| | | |
Collapse
|
7
|
Espinosa-Garcia J, Corchado JC. Analytical Potential Energy Surface and Kinetics of the NH3 + H → NH2 + H2 Hydrogen Abstraction and the Ammonia Inversion Reactions. J Phys Chem A 2010; 114:4455-63. [DOI: 10.1021/jp1001513] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - J. C. Corchado
- Departamento de Química Física, Universidad de Extremadura, Spain
| |
Collapse
|
8
|
Owono Owono LC, Jaidane N, Kwato Njock MG, Ben Lakhdar Z. Theoretical investigation of excited and Rydberg states of imidogen radical NH: Potential energy curves, spectroscopic constants, and dipole moment functions. J Chem Phys 2007; 126:244302. [PMID: 17614544 DOI: 10.1063/1.2741260] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A search is conducted for the calculation of potential energy curves (PECs), spectroscopic constants, and dipole moment functions for excited and Rydberg states of imidogen radical NH, with a particular emphasis on the Rydberg states arising from 3s configuration of nitrogen and 2s and 2p configurations of hydrogen. A range of about 11 eV above the electronic ground state X (3)Sigma- atomic separation limit which corresponds to the first eight asymptotes of dissociation is spanned. Computations are carried out at the internally contracted multireference singles plus doubles configuration interaction level of theory, including the Davidson correction to account for quadruple excitations. The Gaussian basis set used has been modified from a standard basis to give a balanced description of valence-Rydberg interactions. States of (1)Sigma-, (1)Pi, (1)Delta, (3)Sigma-, (3)Pi, (3)Delta, and (5)Sigma- symmetries are computed accurately in the range of energy investigated. PECs of the three lowest (5)Pi states are obtained for the first time. Our spectroscopic constants show good agreement with experimental data in comparison with other theoretical studies reported in the literature. A discussion on the variations of dipole moment functions helps to understand the strong interactions between excited and Rydberg states as well as the avoided crossings. The present study may be of great practical interest for investigations in astrophysical research as well as in laboratory experiments.
Collapse
Affiliation(s)
- L C Owono Owono
- Département de Physique, Ecole Normale Supérieure, Université de Yaoundé I, Boîte Postale 47, Yaoundé, Cameroun.
| | | | | | | |
Collapse
|
9
|
Leach S, Jochims HW, Baumgärtel H. VUV Photodissociation of ammonia: a dispersed fluorescence excitation spectral study. Phys Chem Chem Phys 2005; 7:900-11. [DOI: 10.1039/b409046m] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
10
|
Affiliation(s)
- J. Espinosa-García
- Departamento de Química Física, Universidad de Extremadura, 06071 Badajoz, Spain
| |
Collapse
|
11
|
|
12
|
Affiliation(s)
- J. Espinosa-García
- Departamento de Química Física, Universidad de Extremadura, 06071 Badajoz, Spain
| | - S. Dóbé
- Chemical Research Center, Hungarian Academy of Sciences, Pusztaszeri u. 59-67, H-1025 Budapest, Hungary
| |
Collapse
|
13
|
Ram RS, Bernath PF, Hinkle KH. Infrared emission spectroscopy of NH: Comparison of a cryogenic echelle spectrograph with a Fourier transform spectrometer. J Chem Phys 1999. [DOI: 10.1063/1.478453] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- R. S. Ram
- Department of Chemistry, University of Arizona, Tucson, Arizona 85719
| | - P. F. Bernath
- Department of Chemistry, University of Arizona, Tucson, Arizona 85719 Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - K. H. Hinkle
- Kitt Peak National Observatory, National Optical Astronomy Observatories, Tucson, Arizona 85726
| |
Collapse
|
14
|
|
15
|
Corchado JC, Espinosa-Garcı́a J. Analytical potential energy surface for the NH3+H↔NH2+H2 reaction: Application of variational transition-state theory and analysis of the equilibrium constants and kinetic isotope effects using curvilinear and rectilinear coordinates. J Chem Phys 1997. [DOI: 10.1063/1.473119] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
16
|
Kehe Su, Xiaoling Hu, Xiuyi Li, Yubin Wang, Zhenyi Web. High-level ab initio calculation and assessment of the dissociation and ionization energies of NH2 and NH3 neutrals or cations. Chem Phys Lett 1996. [DOI: 10.1016/0009-2614(96)00677-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
17
|
|