Effect of rotational quantum states (J=0, 1) of matrix H2 molecules on ESR spectra of radicals at 4.2 K

EPR Line-shape Anisotropy and Hyperfine Shift of Methyl Radicals in Solid Ne, Ar, Kr, and p-H2 Gas Matrices

“…As was described previously, 3 the deuterated methyl radical in Ar at 4.2 K was restricted to a ground-level quantum rotation corresponding to an antisymmetric (nuclear-spin) X (rotational) state, giving an EPR singlet instead of the classical septet that they obtained in their work. 5 Similarly, at very low temperatures, narrow EPR transitions for the CH 3 radical measuring about 0.1-0.2 G could be observed in Ar and Ne matrices by Dmitriev. 6 Dmitriev and Zhitnikov have also observed a width of 0.15 G in Kr matrix 4 for the narrowest line M F ) 1/2, while the width of 0.1 G for the M F ) -1/2 transition was observed by Dmitriev in Ne matrix, figure 4 in ref 6.…”

“…This observation suggests that one has to investigate if the quantum properties of the molecular hydrogen matrix have special effects on the EPR spectral anisotropy of the hosted CH 3 radical. It is expected, for example, that quantum rotation and tunneling effects of the hydrogen molecules of the matrix should be more severe than the quantum properties of the CH 3 radical …”

Ориентационная Динамика Метильного Радикала И Матричных Молекул В Твердых Метанах, CH-=SUB=-4-=/SUB=- И CD-=SUB=-4-=/SUB=-, При Криогенных Температурах

“…В результате ориентационная подвижность молекулы метана оказывается промежуточной между почти свободным вращением молекул в твердых водородах и гармоническими осцилляциями в твердом азоте. Такое же соответствие наблюдается и для стабилизированных метильных радикалов: изотропный полностью усредненный вращением [19,20], близким к свободному, спектр ЭПР CH 3 в твердом водороде в сравнении с фиксацией оси третьего порядка в твердом N 2 и возможностью переориентации этой оси в метанах.…”

Electron spin resonance spectroscopy of molecules in large precessional motion: A case of and in solid parahydrogen

“…Second, since p-H 2 has no nuclear spin moment, line broadening due to superhyperfine interaction can be avoided using purified p-H 2 matrix [16][17][18]. We have reported highly resolved ESR lines of H [16], CH 3 [18], C 2 H 5 [17], e À [19,20], and H 6 þ [20-23] in solid p-H 2 .…”

“…Solid para-H 2 (p-H 2 ) is the ideal matrix for high-resolution ESR spectroscopy [15][16][17][18][19][20][21][22][23][24] for two reasons, as follows: first, p-H 2 molecules in solid p-H 2 have large zero-point vibrational motion due to their light mass and small intermolecular interactions, which repairs cracks, distortions, and imperfections, which thus keep the solid highly homogeneous without annealing [6,7,[15][16][17]. Second, since p-H 2 has no nuclear spin moment, line broadening due to superhyperfine interaction can be avoided using purified p-H 2 matrix [16][17][18]. We have reported highly resolved ESR lines of H [16], CH 3 [18], C 2 H 5 [17], e À [19,20], and H 6 þ [20-23] in solid p-H 2 .…”