Linewidth effects

Ci-C6 alkanes/interactions among guest molecules H MAS NMR linewidths (effect of molecular motion on MAS line narrowing) [198]... 

The alternating linewidth effect arises because hyperfine couplings fluctuate due to some inter- or intramolecular process. Selective broadening of the lines in the... 

In Reference 4, this "alternating linewidth" effect (8) was shown to be consistent with a temperature dependent pseudorotation in Kj. A correlation diagram, which relates transition fields for the three obtuse angled trimer geometries, qualitatively predicts line broadening for M = + and h when pseudorota-... 

Secondly, the EPR method is also appropriate to study inverse mixed-valency , involving metal-bridged ligands of different redox states.In those cases, the hopping of unpaired electrons may be noted through linewidth effects as for system [Ru(abpy)2(bpy)] (10). ... 

INDO calculations of coupling constants. ) Assignment may be reversed. ) Determination of barrier to internal rotation by analysis of linewidth effects between 373 and 610 K. ... 

Determination of barrier to internal rotation by analysis of linewidth effects between 373 and 610 K. 

Alternating linewidth effect due to ring inversion. Similar a-values obtained as at 303 K. 

Determination of dissociation enthalpy. Broad ENDOR signals, dynamic line-shape effects. 2 ) da/dr=1.5-10- TK-h Assignment to molecular positions not established experimentally. Broad ENDOR signals. Inequivalence observed at low temperatures — 0.455 mX (2H) at 210 K, alternating linewidth effects. ... 

Experimentally this has been found in dhcp Pr (Houmann et al. 1979, Jensen 1976) and PrAlj (Purwins et al. 1976). Various theoretical methods have been used to describe mixed-mode excitations pseudospon techniques, (Elliott et al. 1972), diagrammatic methods (Thalmeier and Fulde 1975) and equation of motion techniques (Morin et al. 1980b, Aksenov et al. 1981). In the RPA all these methods lead to mixed excitations of infinite lifetime. Lifetime effects can be included in a phenomenological manner, see, e.g., Becker et al. (1981). For a microscopic treatment of linewidth effects beyond RPA the projection operator technique is more suitable (Huggins et al. 1984). 

This is a consequence of reducing the lifetime of a particular spin state an analysis of the lineshape yields the rate constant k2, which equals k-2. Radicals able to undergo conformational change show a spectral phenomenon called the alternating linewidth effect. A temperature-dependence study of this effect will yield activation parameters [energy and entropy, Eq. (2)] for this first-order process. 

C,oH2,02Pb]- H3C OPb(CH2CH3)3 / C-C / 0 CH3 With alternating linewidth effect. Phot, of cyclopentadienyltriethyl-lead in the presence of biacetyl/ Toluene EPR/ 240 2.0053 6H(CH3) 0.67 82Davl... 

Apparently trans derivative [82Davl]. 41 M Pb) Q QQ275 mT K dT With alternating linewidth effect. ... 

With alternating linewidth effect. Conditions of rapid exchange. Also phot, of hexamethylditin in the presence of biacetyl. Also other generations. ... 

INDO calculations. =11.3 kJ-moP for methyl rotation 0.01 n Temperature dependence and linewidth effects ilso [80Sur2 aol . ] ) Further hfs observed. ... 

Linewidth effects studied barrier to pseudorotation c 28kJ-mol ... 

Linewidth effects studied barrier to rotation about C—CHj 8.56 kJ mol Two slightly inequivalent hydrogen pairs. 206 Further hfs observed. ... 

Linewidth effects and relaxation time studies have been very extensive in this field. These are, of course, primarily studies of rates, which are not my present... 

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