Title: Time-dependent view of an isotope effect in electron-nuclear nonequilibrium dynamics with applications to N ₂

Abstract

Isotopic fractionation in the photodissociation of N ₂ could explain the considerable variation in the ¹⁴ N/ ¹⁵ N ratio in different regions of our galaxy. We previously proposed that such an isotope effect is due to coupling of photoexcited bound valence and Rydberg electronic states in the frequency range where there is strong state mixing. We here identify features of the role of the mass in the dynamics through a time-dependent quantum-mechanical simulation. The photoexcitation of N ₂ is by an ultrashort pulse so that the process has a sharply defined origin in time and so that we can monitor the isolated molecule dynamics in time. An ultrafast pulse is necessarily broad in frequency and spans several excited electronic states. Each excited molecule is therefore not in a given electronic state but in a superposition state. A short time after excitation, there is a fairly sharp onset of a mass-dependent large population transfer when wave packets on two different electronic states in the same molecule overlap. This coherent overlap of the wave packets on different electronic states in the region of strong coupling allows an effective transfer of population that is very mass dependent. The extent of the transfermore » depends on the product of the populations on the two different electronic states and on their relative phase. It is as if two molecules collide but the process occurs within one molecule, a molecule that is simultaneously in both states. An analytical toy model recovers the (strong) mass and energy dependence.« less

Authors:

Ajay, Jayanth S.; Komarova, Ksenia G. ;

• Search DOE PAGES for author "Komarova, Ksenia G."
• Search DOE PAGES for ORCID "0000-0001-6603-1377"

Remacle, Francoise; Levine, R. D.

Publication Date:

Mon May 21 00:00:00 EDT 2018

Research Org.:

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

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1438082

Alternate Identifier(s):

OSTI ID: 1540294

Grant/Contract Number:  

SC0012628; T.0132.16; J.0012.18; CM 1405 MOLIM

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 115 Journal Issue: 23; Journal ID: ISSN 0027-8424

Publisher:

National Academy of Sciences, Washington, DC (United States)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Science & Technology; Other Topics; diabatic electronic states; nuclear phase; electronic coherence; photodissociation; nonstationary states