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Title: Infrared spectroscopy and photochemistry of NCCN{sup +} and CNCN{sup +} trapped in solid neon

Abstract

When a Ne:NCCN sample is codeposited at 4.3 K with neon atoms that have been excited in a microwave discharge, the infrared and near infrared spectra of the resulting deposit include a prominent peak at 1799.5 cm{sup -1}, previously assigned to {nu}{sub 3} of NCCN{sup +}, and several new absorptions at higher frequencies which are contributed by combination bands of ground-state NCCN{sup +}. The exposure of the deposit to near infrared and red light results in the appearance of two new absorptions which are attributed to CNCN{sup +}. The reverse isomerization occurs when the sample is exposed to near ultraviolet radiation, but the two new absorptions are regenerated upon subsequent irradiation with near infrared and red light.

Authors:
;  [1]
  1. Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8441 (United States)
Publication Date:
OSTI Identifier:
20991214
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 126; Journal Issue: 5; Other Information: DOI: 10.1063/1.2433945; (c) 2007 U.S. Government; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; ABSORPTION; ABSORPTION SPECTROSCOPY; CYANOGEN; GROUND STATES; HIGH-FREQUENCY DISCHARGES; INFRARED SPECTRA; IRRADIATION; ISOMERIZATION; NEAR ULTRAVIOLET RADIATION; NEON; PHOTOCHEMISTRY

Citation Formats

Jacox, Marilyn E., and Thompson, Warren E.. Infrared spectroscopy and photochemistry of NCCN{sup +} and CNCN{sup +} trapped in solid neon. United States: N. p., 2007. Web. doi:10.1063/1.2433945.
Jacox, Marilyn E., & Thompson, Warren E.. Infrared spectroscopy and photochemistry of NCCN{sup +} and CNCN{sup +} trapped in solid neon. United States. doi:10.1063/1.2433945.
Jacox, Marilyn E., and Thompson, Warren E.. Wed . "Infrared spectroscopy and photochemistry of NCCN{sup +} and CNCN{sup +} trapped in solid neon". United States. doi:10.1063/1.2433945.
@article{osti_20991214,
title = {Infrared spectroscopy and photochemistry of NCCN{sup +} and CNCN{sup +} trapped in solid neon},
author = {Jacox, Marilyn E. and Thompson, Warren E.},
abstractNote = {When a Ne:NCCN sample is codeposited at 4.3 K with neon atoms that have been excited in a microwave discharge, the infrared and near infrared spectra of the resulting deposit include a prominent peak at 1799.5 cm{sup -1}, previously assigned to {nu}{sub 3} of NCCN{sup +}, and several new absorptions at higher frequencies which are contributed by combination bands of ground-state NCCN{sup +}. The exposure of the deposit to near infrared and red light results in the appearance of two new absorptions which are attributed to CNCN{sup +}. The reverse isomerization occurs when the sample is exposed to near ultraviolet radiation, but the two new absorptions are regenerated upon subsequent irradiation with near infrared and red light.},
doi = {10.1063/1.2433945},
journal = {Journal of Chemical Physics},
number = 5,
volume = 126,
place = {United States},
year = {Wed Feb 07 00:00:00 EST 2007},
month = {Wed Feb 07 00:00:00 EST 2007}
}
  • NO{sub 3} can be stabilized in solid neon either by codeposition at 4.3 K of a Ne:O{sub 2} mixture with a Ne:NO mixture that has been passed through a microwave discharge or, in higher yield, by codeposition of a Ne:NO mixture with a Ne:O{sub 2} mixture, followed by annealing of the deposit at {approx}7 K and exposure of the solid to near ultraviolet radiation. All of the previously reported bands of NO{sub 3} between 700 and 3000 cm{sup -1} were observed, most with neon-matrix shifts of less than 2.5 cm{sup -1}. The infrared spectra of eight isotopic species of NO{submore » 3} were obtained. The observed isotopic shifts demonstrate the occurrence of extensive mixing of ground-state levels of e{sup '} symmetry and their strong vibronic interaction with the B-tilde{sup 2}E{sup '} state. Photodissociation of NO{sub 3} by irradiation of the deposit at wavelengths longer than 520 nm leads to new absorptions near the fundamentals of NO and O{sub 2} and other new absorptions at relatively low frequencies. These absorptions were depleted and NO{sub 3} regenerated by subsequent near ultraviolet irradiation of the deposit, suggesting the stabilization of a weakly bound NO(O{sub 2}) complex in solid neon.« less
  • When a mixture of ClCN or BrCN with a large excess of neon is codeposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid includes prominent absorptions of the uncharged isocyanide, ClNC or BrNC, and of the corresponding cation, ClCN{sup +} or BrCN{sup +}. The NC-stretching fundamentals of the isocyanides trapped in solid neon lie close to the positions for their previously reported argon-matrix counterparts. The CN-stretching absorptions of ClCN{sup +} and BrCN{sup +} and the CCl-stretching absorption of ClCN{sup +} appear very close tomore » the gas-phase band centers. Absorptions of two overtones and one combination band of ClCN{sup +} are identified. Reversible photoisomerization of ClCN{sup +} to ClNC{sup +} occurs. The two stretching vibrational fundamentals and several infrared and near infrared absorptions associated with electronic transitions of ClNC{sup +} are observed. Minor infrared peaks are attributed to the vibrational fundamental absorptions of the CX and CX{sup +} species (X=Cl,Br)« less
  • The infrared spectrum of a molecular ion provides a unique signature for that species, gives information on its structure, and is amenable to remote sensing. It also serves as a comparison standard for refining ab initio calculations. Experiments in this laboratory trap molecular ions in dilute solid solution in neon at 4.2 K in sufficient concentration for observation of their infrared spectra between 450 and 4000 cm{sup !1}. Discharge-excited neon atoms produce cations by photoionization and/or Penning ionization of the parent molecule. The resulting electrons are captured by other molecules, yielding anions which provide for overall charge neutrality of themore » deposit. Recent observations of ions produced from C{sub 2}H{sub 4} and BF{sub 3} will be discussed. Because of their relatively large possibility of having low-lying excited electronic states, small, symmetric molecular cations are especially vulnerable to breakdown of the Born-Oppenheimer approximation. Some phenomena which can result from this breakdown will be discussed. Ion-molecule reaction rates are sufficiently high that in some systems absorptions of dimer cations and anions are also observed. When H{sub 2} is introduced into the system, the initially-formed ion may react with it. Among the species resulting from such ion-molecule reactions that have recently been studied are O{sub 4}{sup +}, NH{sub 4}{sup +}, HOCO{sup +}, and HCO{sub 2}{sup !}.« less
  • Laser-ablated Rh{sub {plus}}, Rh, and electrons react with CO on condensation in excess neon at 4 K to form RhCO{sup {plus}}, RhCO, RhCO{sub {minus}}, and Rh(CO){sub 2}{sup {plus}}, Rh(CO){sub 2}, Rh(CO){sub 2}{sup {minus}}, and higher carbonyls. These rhodium carbonyls are identified by isotopic substitution ({sup 13}CO, C{sup 18}O, and mixtures), electron trapping with added CCl{sub 4}, and comparison with DFT calculations of isotopic frequencies. This is the first spectroscopy of isolated rhodium carbonyl cations and anions. The isolated monocarbonyl species provide a scale to estimate local charge on Rh(CO) sites in catalyst systems.
  • Laser-ablated uranium atoms have been reacted with CO molecules during condensation with neon at 4 K. Absorptions at 1,047.3 and 872.2 cm{sup {minus}1} are assigned to the CUO molecule formed from the insertion reaction that requires activation energy. Isotopic substitution shows that the upper band is largely u-C and the lower band mostly U-O in vibrational character. Absorptions at 2,051.5, 1,361.8, and 841.0 cm{sup {minus}1} are assigned to the OUCCO molecule, which is formed by the CO addition reaction to CUO and ultraviolet-visible photon-induced rearrangement of the U(CO){sub 2} molecule. The OUCCO molecule undergoes further photochemical rearrangement to the (C{submore » 2})UO{sub 2} molecule, which is characterized by symmetric and antisymmetric OUO stretching vibrations at 843.2 and 922.1 cm{sup {minus}1}. The uranium carbonyls U(CO){sub x} (x = 1--5) anions, which are formed by electron capture. Relativistic density functional theoretical calculations have been performed for the aforementioned species, which lend strong support to the experimental assignments of the infrared spectra. It is predicted that CUO is a linear singlet molecule with the shortest U-C bond yet characterized, and it has a U-C triple bond with substantial U 5f character. The theoretical analysis also finds that a distorted tetrahedral geometry of (C{sub 2})UO{sub 2} lies much lower in energy than either the bent/linear OUCCO structures or the U(CO){sub 2} uranium dicarbonyl.« less