General cases of the pseudoquadrupole interaction in169Tm

Clauser and Mössbauer [1] showed that the second order (in perturbation theory) magnetic hyperfine interaction, the so called pseudoquadrupole inter-action, in the¹⁶⁹Tm Mössbauer effect can produce apparent isomer shifts. While they assumed two isolated singlets and simplified the coupling, we will show that the second order magnetic hyperfine coupling can be observed in general for any kind of crystalline electric field (CEF) wavefunctions, and that the coupling between many states must often be considered in calculating it. Furthermore since the first order magnetic coupling of the excited CEF states is important, the interaction is best accounted for by diagonalization of the full magnetic hyperfine and CEF Hamiltonian. Examples of the effects that may occur are presented.Work supported by the U. S. Department of Energy.     

A comparative study of side-band Fresnel holograms recorded with self-imaging and general objects

This paper deals with new results obtained in regard to the reconstruction properties of side-band Fresnel holograms (SBFH) of self-imaging type objects (for example, gratings) as compared with those of general objects. The major finding is that a distribution I₂, which appears on the real-image plane along with the conventional real-image I₁, remains a 2Z distribution (where 2Z is the axial distance between the object and its self-imaging plane) under a variety of situations, while its nature and focusing properties differ from one situation to another. It is demonstrated that the two distributions I₁ and I₂ can be used in the development of a novel technique for image subtraction.     

Scientific legacy of Stanley Ruby

Stanley L. Ruby (1924–2004) made major contributions to Mössbauer spectroscopy and was the first to suggest the feasibility of observing the Mössbauer effect using synchrotron radiation. In this article we recall his scientific legacy that have inspired his scientific colleagues.     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Langevin dynamic simulation of hysteresis in a field-swept Landau potential

Numerical simulations are done of Langevin dynamics for a uniform-orderparameter, field-swept Landau model,= –|a/2|m ²+|b/4|m ⁴–mh(t) , to study hysteresis effects. The field is swept at a constant rateh(t)=h(0)+ht. The stochastic jump values of the field {h_J from an initially prepared metastable minimumm(0) are recorded, on passage to a global minimum m(). The results are: (a) The mean jump¯h _J(h) increases (hysteresis loop widens) with h, confirming a previous theoretical criterion based on rate competition between field-sweep and inverse mean first-passage time (FPT); (b) The broad jump distribution(h _J,h) is related to intrinsically large FPT fluctuations ( ²–²)/ ² O(1), and can be quantitatively understood. Possible experimental tests of the ideas are indicated.     

EXAFS study of iron monomers and dimers isolated in solid argon

We report a study of local structure of iron monomers and dimers isolated in a rare gas Ar matrix using extended X-ray absorption fine structure measurements. The results have been compared with Mössbauer measurements on such systems. The interatomic distance found for Fe₂ in these measurements is 1.87 ± 0.13 Å.