Hyperfine Coupling Constants. Electronic g Factor

6 Electronic g Factor. Hyperfine (hf) Coupling Constants Experimental Results 

The g factors and the majority of hf coupling constants come from ESR spectra (see p. 253) of NFg in the gaseous [1,2] and liquid [2] states, in solution [3], molecular sieves [4], and inert gas matrices [5 to 8]. One set of and F hf coupling constants was obtained from an analysis of the multiplets involving low rotational quantum numbers, N=1 to 4, in the microwave spectrum of NFg at 333 to 343 K (see p. 252) [9]. 

The g-tensor elements were calculated by a modified ab initio UHF method ( Nesbet ) [11], by a semiempirical SCF-MO calculation (integral approximations) [12], and by a semiempirical procedure called the energy weighted maximum overlap model [13]. 

The constants ajso(N) and ajso(F) were obtained by a number of ab initio studies UHF ( Nesbet ) [14], UHF and UHFASA [15 to 19], comparison of the UHF, PUHF, PO, and SECI methods [20], RHF + CI [19], and some semiempirical calculations MNDO [21], MINDO within UHF and UHFASA formalisms [22], and INDO (s-electron spin densities aiso/a ef only given, see p. 233) [23]. 

The bjj s were calculated by the ab initio UHF ( Nesbet ) [14] and UHF and UHFASA [15,16] methods. The largest component, b x, was obtained (but p-electron spin density bxx/bret only given, see p. 233) from semiempirical MO (integral approximations) [12] and INDO [23] calculations and by the extended Hiickel method [24, 25]. 

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The quantitative theory of CIDNP [93-96] is developed to a state where the intensity ratios of CIDNP spectra can be computed on the basis of reaction and relaxation rates and the characteristic parameters of the radical pair (initial spin multiplicity, p) the individual radicals (electron g factors, hyperfine coupling constants, a) and the products (spin-spin coupling constants, J). On the other hand, the patterns of signal directions and intensities observed for different nuclei of a reaction product can be interpreted in terms of the hyperfine coupling constants of the same nuclei in the radical cation intermediate. 

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