Neutron dipoles

The physical data index summarizes the quantitative data given for specific compounds in the text, tables and figures in Volumes 1-7. It does not give any actual data but includes references both to the appropriate text page and to the original literature. The structural and spectroscopic methods covered include UV, IR, Raman, microwave, MS, PES, NMR, ORD, CD, X-ray, neutron and electron diffraction, together with such quantities as dipole moment, pX a, rate constant and activation energy, and equilibrium constant. 

The magnetic field seen by the probe neutron is solely due to the magnetic dipole moment density of the unpaired electrons. In other words, the magnetisation density is simply related to the electron spin density by a multiplicative factor, and there is no ambiguity in its definition. 

Figure 5. Model spectra of a naked neutron star. The emitted spectrum with electron-phonon damping accounted for and Tsurf = 106 K. Left panel uniform surface temperature right panel meridional temperature variation. The dashed line is the blackbody at Tsurf and the dash-dotted line the blackbody which best-fits the calculated spectrum in the 0.1-2 keV range. The two models shown in each panel are computed for a dipole field Bp = 5 x 1013 G (upper solid curve) and Bp = 3 x 1013 G (lower solid curve). The spectra are at the star surface and no red-shift correction has been applied. From Turolla, Zane and Drake (2004).

Giant dipole resonance. Isovector giant resonances contain information about the SE through the restoring force. In particular the excitation of the isovector giant dipole resonance (GDR) with isoscalar probes has been used to extract A R/R [32], In the distorted wave Bom approximation optical model analysis of the cross section the neutron and proton transition densities are needed as an input. For example, in the Goldhaber-Teller picture these are... 

We note that also other types of isovector giant resonances have been suggested as a source of information on the neutron skin, such as the spin-dipole giant resonance [33] and the isobaric analog state [34], At present studies of these reactions have not led to quantitative constraints for the neutron skin of... 

It is noteworthy that the neutron work in the merging region, which demonstrated the statistical independence of a- and j8-relaxations, also opened a new approach for a better understanding of results from dielectric spectroscopy on polymers. For the dielectric response such an approach was in fact proposed by G. Wilhams a long time ago [200] and only recently has been quantitatively tested [133,201-203]. As for the density fluctuations that are seen by the neutrons, it is assumed that the polarization is partially relaxed via local motions, which conform to the jS-relaxation. While the dipoles are participating in these motions, they are surrounded by temporary local environments. The decaying from these local environments is what we call the a-process. This causes the subsequent total relaxation of the polarization. Note that as the atoms in the density fluctuations, all dipoles participate at the same time in both relaxation processes. An important success of this attempt was its application to PB dielectric results [133] allowing the isolation of the a-relaxation contribution from that of the j0-processes in the dielectric response. Only in this way could the universality of the a-process be proven for dielectric results - the deduced temperature dependence of the timescale for the a-relaxation follows that observed for the structural relaxation (dynamic structure factor at Q ax) and also for the timescale associated with the viscosity (see Fig. 4.8). This feature remains masked if one identifies the main peak of the dielectric susceptibility with the a-relaxation. 

A giant dipolar resonance (GDR) exists in the majority of photoabsorption and photonuclear reactions. This resonance energy corresponds to the fundamental frequency for absorption of electric dipole radiation by the nucleus acting as a whole. It can be envisioned as an oscillation of neutrons against the protons in a nucleus. The GDR occurs at energies of 20-24 MeV in light material and of 13-15 MeV in heavy nuclei. A compendium of the GDR parameters is found in Ref [3]. 

The atomic dipole moment can be attributed to the preferential population of specific nonspherical atomic orbitals. In particular, this is the case for atoms with doubly-filled nonbonding lone-pair orbitals, such as the oxygen atoms in C—O—H and H—O—H, or oxygen in a terminal position as it is in the carbonyl group. An early demonstration of the bias introduced in X-ray positions of non-hydrogen atoms was the combined X-ray and neutron study of oxalic acid dihydrate (Coppens et al. 1969), which showed the X-ray positions of the oxygen atoms to be systematically displaced by small amounts into the direction of the lone pair density. 

X-ray dipole moments of formamide, of sulfamic acid, of benzene chromium tricarbonyl, and of water, obtained from /c-refinements, are in good agreement with those from other physical techniques. When hydrogen-atom positions are of crucial importance, as in the case of the water molecule, the availability of positional information from neutron diffraction becomes essential if accurate moments are to be obtained. In other cases, extension of the X-H bond to accepted values provides a reasonable alternative. 

However, it seems that possibilities of this model to explain some of the experimental results were not fully explored. Also, this model shows some weaknesses. First, it predicts a value of Tc in DKDP (310 K) that is higher than the experimental value (229 K). Second, the calculated rate of the proton transfer in the PE phase is too low to explain the width of the CP in the neutron scattering spectra of KDP [62]. Third, and most important, because the model assumes that dipoles of PO4 groups lie along the c-axis, it cannot to explain static and dynamic properties of the transverse polarization fluctuations, whose importance in the phase transition mechanism has been supported by several experimental results [8,20,28,31-33]. 

After discovery of the combined charge and space parity violation, or CP-violation, in iT°-meson decay [7], the search for the electric dipole moments (EDMs) of elementary particles has become one of the most fundamental problems in physics [6, 8, 9, 10, 1]. A permanent EDM is induced by the weak interaction that breaks both the space symmetry inversion and time-reversal invariance [11]. Considerable experimental effort has been invested in probing for atomic EDMs induced by EDMs of the proton, neutron and electron, and by P,T-odd interactions between them. The best available restriction for the electron EDM, de, was obtained in the atomic T1 experiment [12], which established an upper limit of de < 1.6 X 10 e-cm, where e is the charge of the electron. The benchmark upper limit on a nuclear EDM is obtained in atomic experiment on i99Hg [13], ]dHgl < 2.1 X 10 e-cm, from which the best restriction on the proton EDM, dp < 5.4 x 10 " e-cm, was also recently obtained by Dmitriev Sen kov [14] (the previous upper limit on the proton EDM was obtained in the TIE experiment, see below). 

Methods covered include X-ray, neutron and electron diffraction, microwave spectroscopy, and their results in terms of molecular dimensions. NMR spectroscopy is treated in some detail as befits its importance, not only proton, but particularly 13C, 15N, and, where appropriate, other nuclei. The section on mass spectrometry briefly covers fragmentation patterns. UV/Fluorescence, IR/Raman, photoelectron spectroscopy, ESR, and dipole moments are covered as appropriate. 

Calculate the magnitude of the magnetic dipole moment vectors of (a) the proton (b) the neutron. 

Magnetic Moment and Spin. Alvarez and Bloch succeeded in measuring the moment of the magnetic dipole associated with the known spin of possessed by the neutron. More refined measurements by Cohen, Corngold, and Ramsey of the magnetic moment p,n yielded a value of... 

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