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Title: Photophysical Dynamics and Relaxation Pathways of Ligand-to-Metal Charge-Transfer States in the 5 f 1 [Np(VI)O 2Cl 4] 2– Anion

Abstract

Although several publications report on the electronic structure of the neptunyl ion, experimental measurements to detail the photophysical dynamics of this open-shell actinyl system are limited in number. Additionally, time-resolved photoluminescence has been a useful experimental approach for understanding photophysical dynamics and relaxation pathways of a variety of other molecular and ionic systems, including gaseous plutonium hexafluoride and solid-state uranyl compounds. Here, we investigate time-resolved photoluminescence emission of the 5f 1 neptunyl tetrachloride ([Np(VI)O 2Cl 4] 2–) dianion following visible excitation. Photoemission of the lowest energy neptunyl ligand-to-metal charge-transfer (LMCT) transitions to both the ground and first electronically excited states is observed. Analyses of the decay lifetimes of the excited states suggest different relaxation pathways as a function of excitation energy. Vibronic progressions associated with the Np-oxo symmetric stretching mode are measured in emission spectra, and the energies from these progressions are compared with energies of vibronic progressions associated with the excitation spectra of [Np(VI)O 2Cl 4] 2–. Here, this study expands our understanding of this open-shell actinyl system beyond identification of excited states, allowing characterization of photophysical properties and evidence for the electronic character of the ground state, and suggests that this approach may be applicable to more complexmore » actinide systems.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1];  [2]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Nevada, Las Vegas, NV (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1505989
Report Number(s):
LA-UR-17-20444
Journal ID: ISSN 1089-5639
Grant/Contract Number:  
89233218CNA000001; AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 121; Journal Issue: 12; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Barker, Beau J., Berg, John M., Kozimor, Stosh Anthony, Wozniak, Nicholas R., and Wilkerson, Marianne Perry. Photophysical Dynamics and Relaxation Pathways of Ligand-to-Metal Charge-Transfer States in the 5f1 [Np(VI)O2Cl4]2– Anion. United States: N. p., 2017. Web. doi:10.1021/acs.jpca.7b01029.
Barker, Beau J., Berg, John M., Kozimor, Stosh Anthony, Wozniak, Nicholas R., & Wilkerson, Marianne Perry. Photophysical Dynamics and Relaxation Pathways of Ligand-to-Metal Charge-Transfer States in the 5f1 [Np(VI)O2Cl4]2– Anion. United States. doi:10.1021/acs.jpca.7b01029.
Barker, Beau J., Berg, John M., Kozimor, Stosh Anthony, Wozniak, Nicholas R., and Wilkerson, Marianne Perry. Tue . "Photophysical Dynamics and Relaxation Pathways of Ligand-to-Metal Charge-Transfer States in the 5f1 [Np(VI)O2Cl4]2– Anion". United States. doi:10.1021/acs.jpca.7b01029. https://www.osti.gov/servlets/purl/1505989.
@article{osti_1505989,
title = {Photophysical Dynamics and Relaxation Pathways of Ligand-to-Metal Charge-Transfer States in the 5f1 [Np(VI)O2Cl4]2– Anion},
author = {Barker, Beau J. and Berg, John M. and Kozimor, Stosh Anthony and Wozniak, Nicholas R. and Wilkerson, Marianne Perry},
abstractNote = {Although several publications report on the electronic structure of the neptunyl ion, experimental measurements to detail the photophysical dynamics of this open-shell actinyl system are limited in number. Additionally, time-resolved photoluminescence has been a useful experimental approach for understanding photophysical dynamics and relaxation pathways of a variety of other molecular and ionic systems, including gaseous plutonium hexafluoride and solid-state uranyl compounds. Here, we investigate time-resolved photoluminescence emission of the 5f1 neptunyl tetrachloride ([Np(VI)O2Cl4]2–) dianion following visible excitation. Photoemission of the lowest energy neptunyl ligand-to-metal charge-transfer (LMCT) transitions to both the ground and first electronically excited states is observed. Analyses of the decay lifetimes of the excited states suggest different relaxation pathways as a function of excitation energy. Vibronic progressions associated with the Np-oxo symmetric stretching mode are measured in emission spectra, and the energies from these progressions are compared with energies of vibronic progressions associated with the excitation spectra of [Np(VI)O2Cl4]2–. Here, this study expands our understanding of this open-shell actinyl system beyond identification of excited states, allowing characterization of photophysical properties and evidence for the electronic character of the ground state, and suggests that this approach may be applicable to more complex actinide systems.},
doi = {10.1021/acs.jpca.7b01029},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
issn = {1089-5639},
number = 12,
volume = 121,
place = {United States},
year = {2017},
month = {3}
}

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