Electron Spin Resonance of Atomic and Molecular Free Radicals Trapped at Liquid Helium Temperature

EPR spectra of deuterated methyl radicals trapped in low temperature matrices

“…The septet has been actually registered in the CD 4 matrix [10] at 4.2 K and solid Ar at 13 K [4]. Though these experimental results are consistent with the above theoretical scheme, another observation has been published [5] for CD 3 in Ar at 4.2 K showing a strong singlet superimposed on a weak septet. The authors explained their results with a new model of a three-dimensional, free quantum rotor with no hindering barrier present.…”

“…5 that at temperatures above 10 K the intensity distribution for CD 3 in Ar is practically «binomial» one, 1:3:6:7:6:3:1, originating not only from the population of J = 0 but also of higher rotational levels. As the temperature was lowered to 4.1 K the central line increased while the other six lines decreased rapidly.…”

“…The experimental spectrum reveals seven strong lines of the CD 3 radical and several weak lines for CH 3 , CH 2 D, and CHD 2 radicals. Superimposed is a record of the high-field lines with a higher gain.…”

“…In explaining the EPR spectrum shape and its transformation, two theoretical approaches are used: one treating the CH 3 radical as a restricted rotor, and another -as a free rotor. In contrast to CH 3 , a few studies have been devoted to deuterated methyl radicals (CD 3 , CH 2 D and CHD 2 ). A spectrum of seven components with «non-binomial» distribution has been predicted for the CD 3 radical [9] at low enough temperatures.…”

“…Methyl radical (CH 3 ) trapped in low-temperature matrices has been extensively studied by EPR [1][2][3][4][5][6][7][8]. It was shown that at low temperatures near 4.2 K, the EPR spectrum of the radical consists of four lines with equal intensity 1:1:1:1, reaching the high-temperature binomial intensity distribution 1:3:3:1 with increasing temperature.…”