An iterative method for the least-squares analysis of an observed high-resolution NMR spectrum is described. The method is applicable even if not all lines are assignable, is not affected by symmetry in the Hamiltonian, yields an estimate of the ellipsoid of error, and converges relatively rapidly to a predetermined assignment. A computer program based on this method is described. Effectively infinite chemical shift may be introduced permitting the analysis of ABXY, etc., spectra. An illustration of its application to the analysis of the proton spectrum of 2-benzoylpyridine is given.

The n.m.r. spectra of 2,2'-bipyridyl (I) in solution in 11 different solvents (CCI4, CCI3H, CHZOH, CzH50H, (CH&CC=CH, CH2ClCH20H, CH&OOH, C2H,COOH, CH3CHBr-COOH, C3H7COOH, CF,COOH) and in binary mixtures of solvents (CCI4-CCI3H, CClr CHIOH, CCLH-CF3COOH) have been recorded and completely analyzed in terms of the fundamental n.m.r. parameters. The n.m.r. spectrum of the iron complex [FeI1(Clo-N2H8)3]CI2 (11) in CH3OH solution has also been recorded and exactly analyzed. The n.m.r. parameters of I show remarkable changes with the nature of solvent used; in particular, the behavior of the chemical shift of the proton 3 (and 3') indicates the existence of a strong deshielding effect exerted by the nitrogen atom of the adjacent ring. The several effects which determine the low-field occurrence of the resonance of protons 3 (and 3') are discussed and their contribution to the shift calculated. It is shown that the van der Waals dispersion forces may cause, at the 3 position, downfield shifts of 0.20-0.30 p.p.m. in the trans-planar conformation of I. As a result of the calculations, different conformations are assigned to 2,2'-bipyridyl in inert and proton donor solvents. The conformations of the mono-and diprotonated cations are also discussed and orders of magnitude of the dihedral angle between the two pyridine rings estimated. The chemical shifts of the protons of I1 are interpreted and calculated in terms of the anisotropy and dispersion force effects which arise because of the relative orientations of the bipyridyl groups in the molecule.

The proton NMR spectra of toluene recorded with and without decoupling of the methyl resonance have been completely analyzed in terms of chemical shifts and coupling constants. The procedures for the analyses of the spectra are illustrated, the results of the different calculations are compared, and the values of the spectral parameters obtained are discussed.

A new search for production of correlated e + e − pairs in the α decay of 241 Am has been carried out deep underground at the Gran Sasso National Laboratory of the I.N.F.N. by using pairs of NaI(Tl) detectors of the DAMA/LIBRA setup. The experimental data show an excess of double coincidences of events with energy around 511 keV in faced pairs of detectors, which are not explained by known side reactions. This measured excess gives a relative activity λ = (4.70 ± 0.63)×10 −9 for the Internal Pair Production (IPP) with respect to alpha decay of 241 Am; this value is of the same order of magnitude as previous determinations. In a conservative approach the upper limit λ < 5.5 × 10 −9 (90% C.L.) can be derived. It is worth noting that this is the first result on IPP obtained in an underground experiment, and that the λ value obtained in the present work is independent on the live-time estimate.

No abstract