Magnesium Transition Research Articles

Оптические сечения поглощения и силы осцилляторов двойного донора магния в кремнии

The optical properties of magnesium impurity in silicon, whose atoms at interstitial positions in the lattice are deep double donors with an ionization energy of 107.56 meV in the neutral state, were studied. For optical transitions from the ground state of a neutral center to the excited levels 2p0 and 2p, the absorption cross sections and oscillator strengths were determined. These parameters were calculated from the impurity absorption spectra that were measured at T  K in samples with different magnesium concentrations. The deep donor content in the samples was determined using Hall effect measurements in the temperature range 78–300 K. The obtained characteristics of intracenter transitions in magnesium were compared with the corresponding literature data for shallow Group V donors in silicon, which are substitutional impurities. It was found that the optical characteristics of the investigated transitions in magnesium are consistent with the dependences of the corresponding parameters on the ionization energy for shallow donors, extrapolated to the region of larger electron binding energies.

Hydrogen induced phase transition in magnesium: An Ab initio study

Abstract Here we report results of Ab initio calculations on phase transitions in bulk magnesium, as well as those occurring upon hydrogenation. The calculations have been carried out within the framework of the FLAPW method. Possible pathways of hydrogen induced phase transitions are discussed.

Accurate laboratory wavelengths of some ultraviolet lines of Cr, Zn and Ni relevant to time variations of the fine structure constant

The quality of astronomical spectroscopic data now available is so high that interpretation and analysis are often limited by the uncertainties of the laboratory data base. In particular, the limit with which space–time variations in the fine structure constant α can be constrained using quasar spectra depends on the availability of more accurate laboratory rest wavelengths. We recently measured some transitions in magnesium by high-resolution Fourier transform spectroscopy for this purpose, and we now report measurements on some ultraviolet resonance lines of Zn ii (2062 and 2026 A), Cr ii (2066, 2062 and 2056 A) and Ni ii (1751, 1741, 1709 and 1703 A). Apart from the last line, which is very weak, the uncertainty of these measurements is 0.002 cm−1 (0.08 ma) for the lines around 2000 A and 0.004 cm−1 (0.12 ma) for the lines around 1700 A.

Isotope Shifts in the Atomic Spectrum of Calcium

The isotope shift in several spectral lines of 40Ca and 48Ca has been measured. A triplet of the arc spectrum shows a specific mass effect a little larger than the normal mass effect and in the opposite direction. In the resonance line and a doublet of the spark spectrum the specific mass shift is very small and in the same direction as the normal shift. Comparison with analogous transitions in magnesium indicates that the specific mass effect shows a similar behaviour in both elements.