Nitrogen hyperfine splitting constants

Fig. 8 (a) Temperature dependence of the nitrogen hyperfine splitting constant of TEMPO and TEMPOL in [bmimHBFJ. (b) Temperature dependence of the nitrogen hyperfine splitting constant of TEMPAMINE in lemimHES]. 

Yonezawa and collaborators (99) have reported unrestricted open-shell SCF calculations where the one-center exchange integrals were taken into account their treatment concerned allyl, vinyl, and nitrogen dioxide radicals. The one-center exchange integrals also are involved in the INDO method (85). Here, the following relationship for hyperfine splitting constants holds ... 

Table 6-5. -Factors and isotropic nitrogen and oxygen hyperfine splitting constants, a( N) and a( 0), of 2,2,6,6-tetramethyl-4-piperidone-l-oxyl in ten solvents of increasing polarity [216],...

Figure 3 Solution spectrum of a typical nitroxide radical where the unpaired electron is mainly interacting (i.e., hyperfine interaction) with the nitrogen nucleus. Since nitrogen is predominantly the isotope, the line is equally split (hyperfine splitting constant) into three (ra/ = - -1, 0, — 1) lines...

Both the chlorine and the bromine data were obtained with die microwave discharge. High concentrations of chlorine and bromine atoms were observed 20 cm. from the discharge after 90 msec, of travel at a pressure of 0.4 mm. of Hg. The chlorine and bromine were found to be almost 100% dissociated when compared to nitrogen dioxide as a quantitative reference. The first derivatives of the absorption curves of plus are shown in Figure 2. The spectra of the two isotopes are easily sorted out from the known natural abundances of CF and The task of sorting out the Br" and Br i spectra was not attempted, since both isotopes are present to about the same extent in bromine and their hyperfine splitting constants are fairly similar. 

In a comprehensive study, adduct radicals formed as a result of the addition of tri-n-butylstannyl radical to triheterapentalenes are investigated. With l,6,6aA -trithiapentalenes, the addition cleaves the S(l)—S(6a) (or S(6)—S(6a)) bonds forming persistent radicals which are detected by ESR and whose g values and hyperfine splitting constants are determined. Whereas selena analogues behave similarly, radical attack on oxygen is not observed for l,6-dioxa-6aA -thiapentalenes, or on nitrogen... 

Knauer and Napier (34e) have suggested a division of current polarity parameters into two classes (I) those that involve no model reaction and which do not probe the solvent at the molecular level (in the cybotactic region) and (2) those that do involve a model and do probe the solvent at the molecular level. As examples of the former class they cite the dielectric constant dipole moment /a, and as examples of the latter class, Y,Z,EtOO) and ft. Nitrogen hyperfine splitting... 

Figure 41 shows the ESR spectrum obtained in tert-butylperoxide initiated polymerization of butadiene. It consists of overlapped Q-line, 3-line, and 3-line spectra, whose splitting patterns are illustrated by stick plots. The 9-line spectrum is a triplet of triplets in which the hyperfine splitting constant is 15.3 G for nitrogen nucleus and 8.40 G for two methylene protons, and it can be assigned to the trapped 1,4 structure 6-11 below. 

Hyperfine splitting constants are proportional to the electron spin density pg, at or near the position of any magnetic nucleus. In the following we T1 report only the Fermi Contact term at the Nitrogen nucleus, which is given by [29]... 

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