SPECTROSCOPY OF THE HYDROGEN AND ANTI-HYDROGEN ATOMS IN EXTERNAL FIELDS

The spectroscopical properties of hydrogen (H) and anti-hydrogen [Formula: see text] atoms in external electric and magnetic fields are discussed. This problem became important in connection with the recent experimental success in production of [Formula: see text] atoms. The main features of these experiments are briefly reviewed. The proposals for the search of the CPT violation via comparison of the H and [Formula: see text] spectra are shortly discussed. The spectroscopical differences between H and [Formula: see text] atoms in external magnetic fields and in parallel magnetic and electric fields are described in detail. It is proven that the positions of the maxima of the frequency distributions for transition probabilities in external electric field for H and [Formula: see text] atoms will deviate if the non-resonant corrections to the Lorentz line profile are taken into account.

Effects of Electron Radiation on the Optical Constants of P-Type Silicon

ABSTRACTThe optical constants n and k are determined for p-type silicon at the Eo and El and critical point energies for one MeV electron irradiated samples. The value for fluences of 1014 and 1016 e−/cm2 are compared to samples before irradiation. The real, ε1 and imaginary,ε2 components of the dielectric function, ε, used to find n and k, were obtained by measurement of tanψ and δ using spectroscopic ellipsometry (SE). The data show that changes in δ, in particular, are greater in the region about Eo than of E1. This is consistent with electrolyte electroreflectance (EER) results in which the Lorentz line shape is narrower for Eo than for E1. The value of n is found to increase and k to decrease with e- radiation at the critical points, although, neither does so monotonically. The change in n at the Eo critical point is greater than at the higher energy main structure E1 whereas, k is a slower varying function in this region.

Synthesis of Critical Point Energies for 1 MeV Electron Irradiated P-Type Silicon

ABSTRACTThe critical point energies, E0, E1 and the Lorentz broadening parameter, Γ, for boron doped p-type silicon were obtained by electrolyte-electroreflectance (EER) at 297K and electron beam electroreflectance (EBER) at 297K and 88K. Electron irradiated samples for fluences of 1014 and 1016 e-/cm2 were compared to the samples before irradiation. The value of the low energy weaker structure, Eo and the higher energy main structure, Ei are obtained by the synthesis of two Lorentz line shapes to fit the experimentally obtained composite spectra. The values as determined by EER were all found to increase with radiation as expected. The values for Eo as found by EBER were consistent with those of EER but those of E1 were not.

An Alternate Approach to Background Correction in Atomic Absorption Spectrometry

An alternate approach to implementing the background correction method originally proposed by Smith and Hieftje has been developed. Its novel feature is that only a single, short duration, high current hollow cathode lamp power pulse is used per measurement cycle. The light from the lamp is measured at the beginning and end of each current pulse after Lorentz line broadening and self-reversal have had time to fully develop. The difference between the absorbance signals observed at the two different sampling intervals is not influenced by either continuum absorption or light-scattering error signals. This approach is simple to implement, uses only standard light sources, possesses the same advantages relative to the conventional auxiliary continuum source lamp method of background correction as does the Smith and Hieftje approach, and has the added feature that all light measurements are made when the source lamp emission is very intense with respect to signals from extraneous light sources.

A New Nonlinear Least Square Algorithm for Voigt Spectral Lines

In this paper a new fitting algorithm which works with Voigt functions is discussed. The fitting algorithm used is an extension of the rapidly convergent gradient method of Fletcher and Powell, who claim faster convergence than the Newton-Raphson method which has been used by Chang and Shaw for fitting Lorentz line widths. The Fletcher and Powell algorithm involves the effects of second derivatives although second derivatives are not explicitly calculated. In our algorithm, first and second derivatives are computed not numerically, but analytically via a modification to Drayson's Voigt function subroutine. This algorithm provides rapid convergence even when there are few data points. Profiles have been fitted with as few as five data points. Our typical line fits involve 40 points. The run time of the algorithm has been compared with the shrinking cube algorithm of Hillman and found to be at least 10 times faster under identical starting conditions. Sample single line and single line plus background are shown illustrating the speed and efficiency of the new algorithm, as well as the importance of good zero-order estimates to start the iterations.