Effective nuclear spin values

The line positions for each /eg are not centred at the field Bq corresponding to the g-factor, but are displaced as shown in the stickplot of Fig. 3.5 for a radical with a large hyperfine coupling of six equivalent I = V2 nuclei (data are for C3F6 in Chapter 5) with effective nuclear spin values, /eff = 0, 1, 2, and 3 which occur 5, 9, 5 and 1 times. The 2 leg +1 hyperfine lines for a specific value of Lg > V2 are not equally spaced but the line splittings increase towards higher fields. The... 

The values of S° represent the virtual or thermal entropy of the substance in the standard state at 298.15 K (25°C), omitting contributions from nuclear spins. Isotope mixing effects are also excluded except in the case of the H—system. 

A feature of the N2 spectrum is an intensity alternation of 1 3 for the J value of the initial level of the transition even odd. This is an effect due to the nuclear spin of the nuclei, which will now be discussed in some detail. 

ESEEM is a pulsed EPR technique which is complementary to both conventional EPR and ENDOR spectroscopy(74.75). In the ESEEM experiment, one selects a field (effective g value) in the EPR spectrum and through a sequence of microwave pulses generates a spin echo whose intensity is monitored as a function of the delay time between the pulses. This resulting echo envelope decay pattern is amplitude modulated due to the magnetic interaction of nuclear spins that are coupled to the electron spin. Cosine Fourier transformation of this envelope yields an ENDOR-like spectrum from which nuclear hyperfine and quadrupole splittings can be determined. 

Mossbauer spectroscopy is based on transition between energy levels of nuclei with different values of the nuclear spin quantum number /. When a nucleus emits a y-ray, the energy of the emitted radiation is lowered by the recoil of the nucleus. Conversely, the energy needed for absorption is higher than that needed for transition, because the absorbing nucleus absorbs energy in the recoil process. For nuclei tightly bound in solids, however, the effective mass of the emitter and... 

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