Title: Time resolved mechanism of the isotope selectivity in the ultrafast light induced dissociation in N ₂

Abstract

The time evolution of a vacuum ultraviolet excited N2 molecule is followed all the way from an ultrafast excitation to dissociation by a quantum mechanical simulation. The primary aim is to discern the role of the excitation by a pulse short compared to the vibrational period, to discern the different coupling mechanisms between different electronic states, nonadiabatic, spin orbit, and to analyze the origin of any isotopic effect. We compare the picture in the time and energy domains. The initial ultrafast excitation pumps the molecule to a coherent electronic wave packet to which several singlet bound electronic states contribute. The total nonstationary wave function is given as a coherent sum of nuclear wave packets on each electronic state times the stationary electronic wave function. When the wave packets on different electronic states overlap, they are coupled in a mass-dependent manner whether one uses an adiabatic or a diabatic electronic basis. A weak spin-orbit coupling acts as a bottleneck between the bound singlet part of phase space and the triplet manifold of states in which dissociation takes place. To describe the spin-orbit perturbation that is ongoing in time, an energy-resolved eigenstate representation appears to be more intuitive. In the eigenstate basis,more » the singlet-to-triplet population transfer is large only between those vibronic eigenstates that are quasiresonant in energy. The states in resonance are different for different excitation energy ranges. Finally, the resonances are mass dependent, which explains the control of the isotope effect through the profile of the pulse.« less

Authors:

Komarova, Ksenia G.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-6603-1377"
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Remacle, Francoise  ^[2];

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• Search DOE PAGES for ORCID "0000-0001-7434-5245"
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Levine, R. D. ^[3]

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+ Show Author Affiliations

1. The Hebrew Univ. of Jerusalem (Israel)
2. The Hebrew Univ. of Jerusalem (Israel); Univ. of Liege, (Belgium)
3. The Hebrew Univ. of Jerusalem (Israel); David Geffen School of Medicine, Los Angeles, CA (United States); Univ. of California, Los Angeles, CA (United States)

Publication Date:

2019-09-19

Research Org.:

Wayne State Univ., Detroit, MI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1611910

Alternate Identifier(s):

OSTI ID: 1562743

Grant/Contract Number:  

SC0012628

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 151; Journal Issue: 11; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; chemistry; physics; spin-orbit interactions; triplet state; isotope effect; photodissociation; coherent states; diabatic states