Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects

M. I. Bagatskii, V. G. Manzhelii, V. V. Sumarokov, A. V. Dolbin, M. S. Barabashko, B. Sundqvist

Research output: Contribution to journal › Article

Abstract

The heat capacity of the interstitial solid solution (CH ₄ )0.4C60 has been investigated in the temperature inter-val 1.4-120 K. The contribution of CH ₄ molecules to the heat capacity of the solution has been separated. The contributions of CH ₄ and CD ₄ molecules to the heat capacity of the solutions (CH ₄ ) _0.40 C ₆₀ and (CD ₄ ) _0.40 C ₆₀ have been compared. It is found that above 90 K the character of the rotational motion of CH ₄ and CD ₄ mole-cules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH ₄ and CD ₄ molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect is due to main-ly, the difference in the frequencies of local translational and libration vibrations of molecules CH ₄ and CD ₄ . The contribution of the tunnel rotation of the CH ₄ and CD ₄ molecules to the heat capacity is dominant be-low 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH ₄ and CD ₄ molecules. The conversion rate of CH ₄ molecules is several times lower than that of CD ₄ ones. Weak features observed in the curves of temperature dependencies of the heat capacity of CH ₄ and CD ₄ molecules near 6 and 8 K, respectively, are most likely a manifestation of first-order polyamorphic phase transitions in the orientational glasses of these solutions.

Original language	English
Pages (from-to)	873-880
Number of pages	8
Journal	Fizika Nizkikh Temperatur
Volume	40
Issue number	8
Publication status	Published - 1 Jan 2014
Externally published	Yes

Fingerprint

isotope effect

methane

specific heat

methylidyne

matrices

molecules

libration

nuclear spin

tunnels

vibration

rotational spectra

interstitials

solid solutions

intervals

temperature

glass

curves

Keywords

Heat capacity
Isotope effects
Nuclear spin species
Rotational dynamics

ASJC Scopus subject areas

Physics and Astronomy(all)

Cite this

Bagatskii, M. I., Manzhelii, V. G., Sumarokov, V. V., Dolbin, A. V., Barabashko, M. S., & Sundqvist, B. (2014). Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects. Fizika Nizkikh Temperatur, 40(8), 873-880.

Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects. / Bagatskii, M. I.; Manzhelii, V. G.; Sumarokov, V. V.; Dolbin, A. V.; Barabashko, M. S.; Sundqvist, B.

In: Fizika Nizkikh Temperatur, Vol. 40, No. 8, 01.01.2014, p. 873-880.

Research output: Contribution to journal › Article

Bagatskii, MI, Manzhelii, VG, Sumarokov, VV, Dolbin, AV, Barabashko, MS & Sundqvist, B 2014, 'Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects', Fizika Nizkikh Temperatur, vol. 40, no. 8, pp. 873-880.

Bagatskii MI, Manzhelii VG, Sumarokov VV, Dolbin AV, Barabashko MS, Sundqvist B. Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects. Fizika Nizkikh Temperatur. 2014 Jan 1;40(8):873-880.

Bagatskii, M. I. ; Manzhelii, V. G. ; Sumarokov, V. V. ; Dolbin, A. V. ; Barabashko, M. S. ; Sundqvist, B. / Low-temperature dynamics of matrix isolated methane molecules in fullerite C ₆₀ . The heat capacity, isotope effects. In: Fizika Nizkikh Temperatur. 2014 ; Vol. 40, No. 8. pp. 873-880.

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abstract = "The heat capacity of the interstitial solid solution (CH 4 )0.4C60 has been investigated in the temperature inter-val 1.4-120 K. The contribution of CH 4 molecules to the heat capacity of the solution has been separated. The contributions of CH 4 and CD 4 molecules to the heat capacity of the solutions (CH 4 ) 0.40 C 60 and (CD 4 ) 0.40 C 60 have been compared. It is found that above 90 K the character of the rotational motion of CH 4 and CD 4 mole-cules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH 4 and CD 4 molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect is due to main-ly, the difference in the frequencies of local translational and libration vibrations of molecules CH 4 and CD 4 . The contribution of the tunnel rotation of the CH 4 and CD 4 molecules to the heat capacity is dominant be-low 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH 4 and CD 4 molecules. The conversion rate of CH 4 molecules is several times lower than that of CD 4 ones. Weak features observed in the curves of temperature dependencies of the heat capacity of CH 4 and CD 4 molecules near 6 and 8 K, respectively, are most likely a manifestation of first-order polyamorphic phase transitions in the orientational glasses of these solutions.",

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N2 - The heat capacity of the interstitial solid solution (CH 4 )0.4C60 has been investigated in the temperature inter-val 1.4-120 K. The contribution of CH 4 molecules to the heat capacity of the solution has been separated. The contributions of CH 4 and CD 4 molecules to the heat capacity of the solutions (CH 4 ) 0.40 C 60 and (CD 4 ) 0.40 C 60 have been compared. It is found that above 90 K the character of the rotational motion of CH 4 and CD 4 mole-cules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH 4 and CD 4 molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect is due to main-ly, the difference in the frequencies of local translational and libration vibrations of molecules CH 4 and CD 4 . The contribution of the tunnel rotation of the CH 4 and CD 4 molecules to the heat capacity is dominant be-low 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH 4 and CD 4 molecules. The conversion rate of CH 4 molecules is several times lower than that of CD 4 ones. Weak features observed in the curves of temperature dependencies of the heat capacity of CH 4 and CD 4 molecules near 6 and 8 K, respectively, are most likely a manifestation of first-order polyamorphic phase transitions in the orientational glasses of these solutions.

AB - The heat capacity of the interstitial solid solution (CH 4 )0.4C60 has been investigated in the temperature inter-val 1.4-120 K. The contribution of CH 4 molecules to the heat capacity of the solution has been separated. The contributions of CH 4 and CD 4 molecules to the heat capacity of the solutions (CH 4 ) 0.40 C 60 and (CD 4 ) 0.40 C 60 have been compared. It is found that above 90 K the character of the rotational motion of CH 4 and CD 4 mole-cules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH 4 and CD 4 molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect is due to main-ly, the difference in the frequencies of local translational and libration vibrations of molecules CH 4 and CD 4 . The contribution of the tunnel rotation of the CH 4 and CD 4 molecules to the heat capacity is dominant be-low 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH 4 and CD 4 molecules. The conversion rate of CH 4 molecules is several times lower than that of CD 4 ones. Weak features observed in the curves of temperature dependencies of the heat capacity of CH 4 and CD 4 molecules near 6 and 8 K, respectively, are most likely a manifestation of first-order polyamorphic phase transitions in the orientational glasses of these solutions.

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