Hydrogen magnetic transitions

Above it was pointed out that in unmixed rare gases binary absorption does not exist because of the inversion symmetry of like pairs. For like molecular pairs inversion symmetry does in general not exist because of the anisotropic structure and vibrational excitations of the individual molecules. In Chapter 5, we will show that in pure hydrogen gas, for example, the translational spectrum arises mainly from orientational ( magnetic ) transitions the translational spectrum of H2-H2 is discernible in Fig. 3.10 at low frequencies (0 < v < 250 cm-1). The translational peak is weak if compared to the strong So(J) lines near 354 and 587 cm-1, but its strength is comparable to those of the dissimilar rare gas pairs, Fig. 3.1. The translational H2-He pair spectra are somewhat stronger, Fig. 3.12,... 

NMR spectroscopy has shown that the allyl ligand in both platinum and rhodium allyl complexes at room temperature in deuterochloroform solution has all terminal hydrogens magnetically equivalent (20). This phenomenon may result from an interchange of the four allyl protons via a short-lived cr-allyl intermediate or transition state. As seen in Fig. 8, for such a rearrangement to take place a rotation around the C(l)-C(2) bond occurs, interchanging protons 1 and 2 concurrent with a rotation around the C(2)-C(3) bond interchanging protons 3 and 4. 

The magnitude and direction of the magnetic moment m, o must be estimated from knowledge of the transition. Usually the molecular transition is related to an atomic hydrogen-like transition. For a hydrogen-like atom the selection rules are ... 

The temperature and thickness dependence of the electric resistivity of Sm, Dy and Tm thin films (25-370 nm thick) was measured between 4.2 and 300 K by Dudas and Feher (1984, 1987), Dudas et al. (1985, 1986, 1987a-d, 1990), and Janos et al. (1987). For Dy films the Neel temperature and the residual resistivity ratio increase both as thickness increases. The thickness dependence of the spin-disorder resistivity is reported in fig. 6. In the case of Tm samples it is observed that the Neel temperature increases (from 49 to 54 K) and in-disorder resistivity decreases (from 35 to lOpQm) as thickness increases (fig. 7). Such results, and correlations with the crystalline orientations (basal plane of crystallites parallel or perpendicular to the substrate surface) correct the errors made by other investigators (see Gasgnier 1980). On the other hand the resistance ratio as a fimction of the temperature exhibits different kinds of curves as the thickness varies as measured for Tm films (fig. 8). Different magnetic transitions have been also observed. One can conclude that numerous kinds of anomalies were caused by hydrogen in solution in the metallic matric, in agreement with Dudas (1991), and also by structure... 

The heat capacity of the semiconducting orthorhombic europium hydride was measured by Drulis and Stalinski (1989) for EuHi.gs and by Drulis (1993) for EuD2, who observed a L-type anomaly for the magnetic transition at Tc=15.8K for the former and at Tc = 16.3 K for the latter (see sect. 6). The T-dependence of Cp above 50K exhibits a marked isotope effect which was analysed by Drulis (1993) on the basis of hydrogen optical modes as determined from infrared absorption spectra. 

The simplest place to start is with a hydrogen atom. The experimental ESR spectrum shows two lines separated by 1420.4 MHz (often reported as a magnetic induction, since transitions occur at the resonance condition hv = In... 

Nuclear magnetic resonance, NMR (Chapter 13 introduction) A spectroscopic technique that provides information about the carbon-hydrogen framework of a molecule. NMR works by detecting the energy absorptions accompanying the transitions between nuclear spin states that occur when a molecule is placed in a strong magnetic field and irradiated with radiofrequency waves. 

Transitions between states are subject to certain restrictions called selection rules. The conservation of angular momentum and the parity of the spherical harmonics limit transitions for hydrogen-like atoms to those for which A/ = 1 and for which Am = 0, 1. Thus, an observed spectral line vq in the absence of the magnetic field, given by equation (6.83), is split into three lines with wave numbers vq + (/ bB/he), vq, and vq — (HbB/he). 

Remarkably, the Wigner distribution could be observed in a number of systems by physical experiments and computer simulations evading the whole quantum world from atomic nuclei to the hydrogen atom in a magnetic field to the metal-insulator transition (Guhr, Muller-Groeling and Weidenmuller, 1998). In this contribution we address the situation in QCD and in hadrons. 

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