Measurement of Electron Spin Resonance Difference Spectra at 77 °k: Applications of the Method in Low-Temperature Radiation Chemistry

Abstract

The technique of measuring e.s.r. difference spectra has been extended to 77 "I<. This enables elimination of the main signal due to irradiated silica sample tubes and of about 90% of the hydrogen atom signal from the same source. Under certain conditions, e.g. when the e.s.r. spectrum due to one species can be photochemically bleached, the method permits resolution of two superimposed spectra. This has been demonstrated by measurements which resolve the e.s.r. singlet due to trapped electrons in irradiated tetrahydro-2-methylfuran from the underlying septet. These develop~~lents have rendered the e.s.r. difference method very useful for the study of paramagnetic species formed in systems which have been 7-irradiated a t 77 'I<.

ELECTRON SPIN RESONANCE SPECTRA OF 15N-CENTERED RADICALS AT LOW TEMPERATURES: II. THE RADIOLYSIS OF POTASSIUM SULFAMATE

“…Dosimetry measurements were made using the ferrous sulfate method (5). The electron spin resonance spectrometer has already been described (6). Conventional methods (7) were used to determine the elements of the hyperfine interaction tensors, a n isotropic g-factor of 2.004 being assumed.…”

“…I t is estimated that reactions [4] and [6] are approxin~ately of equal importance in the recombination of NHzS03 and e-. Reaction [5] accounts for the absence of trapped hydrogen atoms and gives rise to further NHS03-.…”

“…(iii) Warming to room temperature.-The untrapping of the electrons must be followed by reactions [4], [5], [6], and [S], since only NHSOB-and SO3-are detected a t room temperature. Since the total radical yield a t 77 OK did not include G(etU), the total radical yield after warming to room temperature (-29s OK) should increase by this amount.…”

An Electron Spin Resonance Study of Trapped Electrons Formed at 77.5 °k by Gamma Irradiation of an Organic Glass

“…Figure 2c is the difference between 2a and 2b obtained by the technique of measuring e.s.r. difference spectra described earlier (8). Figure 3 is the same as Fig.…”

“…difference spectrum technique. This technique and the procedure for the preparation and handling of M T H F samples have been described previously (8). The scan rate was calibrated using the major hyperhne splitting of the tetracene positive ion (9).…”