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Title: Dynamics of Methane Trapped in C(60) Interstices

Abstract

In order to understand the hindered rotational and vibrational dynamics of methane trapped in C{sub 60} interstices and to determine the structure around the interstitial site, they have carried out inelastic neutron scattering studies of the methane/C{sub 60} system. At temperatures of 20K and below, they observe inelastic peaks from rotational transitions of the CH{sub 4}. These transitions allow unambiguous assignment of the hindered rotational energy levels and a determination of the interaction potential. The appearance of two peaks for one of the J = 0{r_arrow}3 transitions implies the existence of two distinct kinds of interstitial sites and the measured transition energies suggest a rotational barrier of about 26 and 16 meV for these sites. Time-dependent changes in peak heights indicate slow t{sub 1/2} ({approx} 2.6 hrs) triplet{r_arrow}quintet nuclear spin conversion that necessarily accompanies the J = 1{r_arrow}0 rotational relaxation. They also have observed a sharp inelastic peak at 9.3 meV, which corresponds to a local vibrational mode of CH{sub 4} rattling in its cage at {approximately} 2.2 THz. Other peaks involving higher-energy vibrational excitations in CD{sub 4}/C{sub 60} correspond in energy to assigned peaks in the inelastic neutron scattering spectra of C{sub 60}, albeit sometimes with different intensities.

Authors:
; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
12669
Report Number(s):
SAND99-2300J
TRN: AH200120%%461
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Other Information: Submitted to Journal of Chemical Physics; PBD: 1 Sep 1999
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; ENERGY LEVELS; INTERSTITIALS; METHANE; NEUTRONS; RELAXATION; SCATTERING; SPECTRA; SPIN

Citation Formats

KING, HARRY F., KWEI, GEORGE H., MOROSIN, BRUNO, and TROUW, FRANS. Dynamics of Methane Trapped in C(60) Interstices. United States: N. p., 1999. Web.
KING, HARRY F., KWEI, GEORGE H., MOROSIN, BRUNO, & TROUW, FRANS. Dynamics of Methane Trapped in C(60) Interstices. United States.
KING, HARRY F., KWEI, GEORGE H., MOROSIN, BRUNO, and TROUW, FRANS. Wed . "Dynamics of Methane Trapped in C(60) Interstices". United States. https://www.osti.gov/servlets/purl/12669.
@article{osti_12669,
title = {Dynamics of Methane Trapped in C(60) Interstices},
author = {KING, HARRY F. and KWEI, GEORGE H. and MOROSIN, BRUNO and TROUW, FRANS},
abstractNote = {In order to understand the hindered rotational and vibrational dynamics of methane trapped in C{sub 60} interstices and to determine the structure around the interstitial site, they have carried out inelastic neutron scattering studies of the methane/C{sub 60} system. At temperatures of 20K and below, they observe inelastic peaks from rotational transitions of the CH{sub 4}. These transitions allow unambiguous assignment of the hindered rotational energy levels and a determination of the interaction potential. The appearance of two peaks for one of the J = 0{r_arrow}3 transitions implies the existence of two distinct kinds of interstitial sites and the measured transition energies suggest a rotational barrier of about 26 and 16 meV for these sites. Time-dependent changes in peak heights indicate slow t{sub 1/2} ({approx} 2.6 hrs) triplet{r_arrow}quintet nuclear spin conversion that necessarily accompanies the J = 1{r_arrow}0 rotational relaxation. They also have observed a sharp inelastic peak at 9.3 meV, which corresponds to a local vibrational mode of CH{sub 4} rattling in its cage at {approximately} 2.2 THz. Other peaks involving higher-energy vibrational excitations in CD{sub 4}/C{sub 60} correspond in energy to assigned peaks in the inelastic neutron scattering spectra of C{sub 60}, albeit sometimes with different intensities.},
doi = {},
journal = {Journal of Chemical Physics},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {9}
}