Low-temperature tunneling of CH₃ quantum rotor in van der Waals solids

• Date: 2019
• Main Authors: Benetis, N.P., Zelenetckii, I.A., Dmitriev, Y.A.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2019
• Series: Физика низких температур
• Subjects: Фізичні властивості кpіокpисталів
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/176095
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Low-temperature tunneling of CH₃ quantum rotor in van der Waals solids / N.P. Benetis, I.A. Zelenetckii, Y.A. Dmitriev // Физика низких температур. — 2019. — Т. 45, № 4. — С. 495-510. — Бібліогр.: 38 назв. — англ.

Motional quantum effects of tunneling methyl radical isolated in solid gases as they appear on experimental electron paramagnetic resonance (EPR) spectra are examined. Obtained analytical expressions of the tunneling frequency for methyl rotor/torsional-oscillator utilizing localized Hermite polynomials are compared to full numerical computations and tested against experimental EPR lineshape simulations. In particular, the X-band of methyl radical was displaying partial anisotropy averaging even at lowest temperatures. EPR lineshape simulations involving rotational dynamics were applied for the accurate determination of the potential barrier and the tunneling frequency. Tunneling frequency, as the splitting between the A and E torsional levels by the presence of a periodic C₃ model potential with periodic boundary conditions, was computed and related to the EPRlineshape alteration. The corresponding C₂ rotary tunneling about the in-plane axes of methyl was also studied while both the C₂ and C₃ rotations were compared with the rotation of deuteriated methyl radical.