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Lykhin AO, Truhlar DG, Gagliardi L. Role of Triplet States in the Photodynamics of Aniline. J Am Chem Soc 2021; 143:5878-5889. [PMID: 33843225 DOI: 10.1021/jacs.1c00989] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamics of excited heteroaromatic molecules is a key to understanding the photoprotective properties of many biologically relevant chromophores that dissipate their excitation energy nonreactively and thereby prevent the detrimental effects of ultraviolet radiation. Despite their structural variability, most substituted aromatic compounds share a common feature of a repulsive 1πσ* potential energy surface. This surface can lead to photoproducts, and it can also facilitate the population transfer back to the ground electronic state by means of a 1πσ*/S0 conical intersection. Here, we explore a hidden relaxation route involving the triplet electronic state of aniline, which has recently been discovered by means of time-selected photofragment translational spectroscopy [J. Chem. Phys. 2019, 151, 141101]. By using the recently available analytical gradients for multiconfiguration pair-density functional theory, it is now possible to locate the minimum-energy crossing points between states of different spin and therefore compute the intersystem crossing rates with a multireference method, rather than with the less reliable single-reference methods. Using such calculations, we demonstrate that the population loss of aniline in the T1(3ππ*) state is dominated by C6H5NH2 → C6H5NH· + H· dissociation, and we explain the long nonradiative lifetimes of the T1(3ππ*) state at the excitation wavelengths of 294-264 nm.
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Affiliation(s)
- Aleksandr O Lykhin
- Department of Chemistry, Pritzker School of Molecular Engineering, The James Franck Institute and Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Laura Gagliardi
- Department of Chemistry, Pritzker School of Molecular Engineering, The James Franck Institute and Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
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Singh DP, De Oliveira N, Garcia GA, Vredenborg A, Powis I. Experimental and Theoretical Investigation of the 3sp(d) Rydberg States of Fenchone by Polarized Laser Resonance-Enhanced-Multiphoton-Ionization and Fourier Transform VUV Absorption Spectroscopy. Chemphyschem 2020; 21:2468-2483. [PMID: 32893958 DOI: 10.1002/cphc.202000365] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 09/04/2020] [Indexed: 11/08/2022]
Abstract
The VUV absorption spectrum of fenchone is re-examined using synchrotron radiation Fourier transform spectrometry, revealing new vibrational structure. Picosecond laser (2+1) resonance enhanced multiphoton ionization (REMPI) spectroscopy complements this, providing an alternative view of the 3spd Rydberg excitation region. These spectra display broadly similar appearance, with minor differences that are largely explained by referring to calculated one- and two-photon electronic excitation cross-sections. Both show good agreement with Franck-Condon simulations of the relevant vibrational structures. Parent ion REMPI ionization yields with both femtosecond and picosecond excitation laser pulses are studied as a function of laser polarization and intensity, the latter providing insight into the relative two-photon excitation and one-photon ionization rates. The experimental circular-linear dichroism observed in the parent ion yields varies strongly between the 3s and 3p Rydberg states, in good overall agreement with the calculated two-photon excitation circular-linear dichroism, while corroborating other evidence that the 3pz sub-state plays no more than a very minor role in the (2+1) REMPI spectrum. Vibrationally resolved photoelectron spectra are recorded with picosecond pulse duration (2+1) REMPI at selected intermediate vibrational excitations. The 3s intermediate state displays a very strong Δv=0 propensity on ionization, but the 3p intermediate evidences more complex vibronic dynamics, and we infer some 3p→3s internal conversion prior to ionization.
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Affiliation(s)
- Dhirendra P Singh
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, U.K
| | - Nelson De Oliveira
- Synchrotron SOLEIL, l'Orme des Merisiers, 91192 Cedex, Saint-Aubin BP 48, Gif-sur-Yvette, France
| | - Gustavo A Garcia
- Synchrotron SOLEIL, l'Orme des Merisiers, 91192 Cedex, Saint-Aubin BP 48, Gif-sur-Yvette, France
| | - Arno Vredenborg
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, Netherlands
- MassSpecpecD BV, Langenkampweg 101, 7522 LL, Enschede, Netherlands
| | - Ivan Powis
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, U.K
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Arlt J, Singh DP, Thompson JOF, Chatterley AS, Hockett P, Stapelfeldt H, Reid KL. Photoelectron angular distributions from resonant two-photon ionisation of adiabatically aligned naphthalene and aniline molecules. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1836411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Jacqueline Arlt
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | | | | | | | - Paul Hockett
- Steacie Institute for Molecular Science, National Research Council of Canada, Ottawa, Canada
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Yifrach Y, Rahimi R, Portnov A, Bar I. A new imaging-based method for alignment of multiple laser beams. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 237:118404. [PMID: 32361520 DOI: 10.1016/j.saa.2020.118404] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 04/20/2020] [Accepted: 04/20/2020] [Indexed: 06/11/2023]
Abstract
A new method for multiple laser beams alignment, useful in a wide range of spectroscopies, is proposed and demonstrated. The method, based on the coupling of spatial map imaging (SMI) with velocity map imaging (VMI), aided beams visualization, through interrogation of the ionization signal of different species in a time-of-flight mass spectrometer. This approach is very effective for alignment and for evaluating the spatial overlap of laser beams with a molecular beam. This was demonstrated by monitoring the resonant two-photon ionization spectrum of 2-phenylethylamine (PEA) monomer and its hydrated (PEA-H2O) cluster and the ionization-loss stimulated Raman spectrum of the cluster, via VMIs accumulation, as a function of the exciting laser wavelength. The former permitted immediate classification of the features in the spectrum, corresponding to the molecular ion or the cluster. The proposed methodology will be useful in other challenging multiple laser beam experiments for spectroscopic studies and is expected to improve extensively their outcome.
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Affiliation(s)
- Yair Yifrach
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Rami Rahimi
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Alexander Portnov
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Ilana Bar
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
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Gutsev GL, López Peña HA, McPherson SL, Boateng DA, Ramachandran BR, Gutsev LG, Tibbetts KM. From Neutral Aniline to Aniline Trication: A Computational and Experimental Study. J Phys Chem A 2020; 124:3120-3134. [PMID: 32233368 DOI: 10.1021/acs.jpca.0c00686] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report density functional theory computations and photoionization mass spectrometry measurements of aniline and its positively charged ions. The geometrical structures and properties of the neutral and singly, doubly, and triply positively charged aniline are computed using density functional theory with the generalized gradient approximation. At each charge, there are multiple isomers closely spaced in total energy. Whereas the lowest energy states of both neutral and cation have the same topology C6H5-NH2, the dication and trication have the C5NH5-CH2 topology with the nitrogen atom in the meta- and para-positions, respectively. We compute the dissociation pathways of all four charge states to NH or NH+ and NH2 or NH2+, depending on the initial charge of the aniline precursor. Dissociation leading to the formation of NH (from the neutral and cation) and NH+ (from the dication and trication) proceeds through multiple transition states. On the contrary, the dissociation of NH2 (from the neutral and cation) and NH2+ (from the dication and trication) is found to proceed without an activation energy barrier. The trication was found to be stable toward abstraction on NH+ and NH2+ by 0.96 and 0.18 eV, respectively, whereas the proton affinity of the trication is substantially higher, 1.98 eV. The mass spectra of aniline were recorded with 1300 nm, 20 fs pulses over the peak intensity range of 1 × 1013 to 3 × 1014 W cm-2. The analysis of the mass spectra suggests high stability of both dication and trication to fragmentation. The formation of the fragment NH+ and NH2+ ions is found to proceed via Coulomb explosion.
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Affiliation(s)
- G L Gutsev
- Department of Physics, Florida A&M University, Tallahassee, Florida 32307, United States
| | - H A López Peña
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - S L McPherson
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - D Ampadu Boateng
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - B R Ramachandran
- Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, United States
| | - L G Gutsev
- Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, United States.,Institute of Problems of Chemical Physics of Russian Academy of Sciences, Chernogolovka, Moscow District 142432, Russia
| | - K M Tibbetts
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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Qu Z, Qin Z, Zheng X, Wang H, Yao G, Zhang X, Cui Z. Slow-electron velocity-map imaging study of aniline via resonance-enhanced two-photon ionization method. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 173:432-438. [PMID: 27705848 DOI: 10.1016/j.saa.2016.09.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 08/31/2016] [Accepted: 09/26/2016] [Indexed: 06/06/2023]
Abstract
Slow electron velocity-map imaging (SEVI) of aniline has been investigated via two-color resonant-enhanced two-photo (1+1') ionization (2C-R2PI) method. A number of vibrational frequencies in the first excited state of neutral (S1) and 2B1 ground electronic state of cation (D0) have been accurately determined. In addition, photoelectron angular distributions (PADs) in the two-step transitions are presented and reveal a near threshold shape resonance in the ionization of aniline. The SEVI spectra taken via various S1 intermediate states provide the detailed vibrational structures of D0 state and directly deduce the accurate adiabatic ionization potential (IP) of 62,271±6cm-1. Ab initio calculations excellently reproduce the experimental IP value (Theo. 62,242cm-1). For most vibrational modes, good agreement between theoretical and experimental frequencies in the S0 and D0 states of aniline is obtained to aid us to clearly assign vibrational modes. Especially, the vibrational frequencies calculated at the CASSCF level are much better consistent with experimental data than that obtained using the TDDFT and CIS methods.
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Affiliation(s)
- Zehua Qu
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Zhengbo Qin
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China.
| | - Xianfeng Zheng
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China.
| | - Hui Wang
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Guanxin Yao
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Xianyi Zhang
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Zhifeng Cui
- Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China
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