A theoretical investigation of the experimentally observed (Stolterfoht N et al 2001 Phys. Rev. Lett. 87 023201) interference effects in the double differential cross sections for ionization of the hydrogen molecule by fast ion impact is reported. The H2/2H cross section ratios as a function of the ejected electron velocity show an oscillating pattern, for which Stolterfoht et al propose a formula C + G sin(k D)/(k D), where k is the electron momentum and D the internuclear separation in H2. Our analysis in its simplest form leads instead to a formula C + G sin(k|| D)/(k|| D) where k|| is the component of k parallel to the projectile velocity. The presented theoretical model thus explains why at 90° the interference pattern will be strongly suppressed. In addition to the simplified analysis a numerical evaluation of a more accurate model is presented, confirming the latter qualitative prediction.

The ionization of H(1s) in superintense, high-frequency, attosecond pulses is studied beyond the dipole approximation. We identify a unique nondipole 3rd lobe in the angular distribution of the ejected electron and show that this lobe has a well-defined classical counterpart. The ionization is likely to occur in the direction opposite to the laser propagation direction, which is fully understood from an analysis of the classical dynamics.

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The Tibetan Plateau has very high levels of ultraviolet radiation. To study the UV radiation across the Tibetan Plateau, data from the TOMS (Total Ozone Mapping Spectrometer) satellite for the periods 1979 -1992 and 1997–¬ 2003 are used. The analysis shows a 21-year average of the spatial distribution of daily summer erythemal UV doses across the Tibetan Plateau and its vicinity with a spatial resolution of 1° Lat. - 1.25° Long., also obtains temporal variations during the period 1979 ¬- 2003 of UV radiation for the region by selecting seven locations across the Tibetan Plateau and its neighboring areas. The results show that during the summer months from May to August the average daily erythemal UV doses at the selected seven sites across the Tibetan Plateau range from 7.5 to 9.0 kJ/m2. These daily erythemal UV doses are considerably higher than those observed at geographically close, lower-altitude locations such as Chengdu in China and New Delhi in India, which had corresponding values of 4.1 kJ/m2 and 5.8 kJ/m2, respectively. During the period from 1979 to 1992 observe a clear trend of increasing erythemal UV doses over the Tibetan Plateau. Comparisons between satellite derived UV radiation and ground-based measurements of UV radiation for Lhasa are made

In recent experiments of single-cycle field ionization of excited Na(nd) atoms with principal quantum number (Li and Jones 2014 Phys. Rev. Lett. 112 143006) it was shown that the maximum field intensity necessary to ionize 10% of the atoms decreases with increasing n according to an power law dependence. This scaling property at the same ionization probability was confirmed in classical trajectory Monte Carlo calculations. In this work we note that the scaling relation in the experiment is much more general, it is in fact valid for all ionization probabilities. When applied to the emitted electron energies it places a very wide distribution of electron momenta from different initial states onto a narrow range. These aspects are investigated in a one-dimensional model with a 3D hydrogen-like spectrum. Calculations confirm the general scaling relation for the ionization probability and that this particular scaling of the kinetic emission spectrum puts the ejected electron momenta on a narrow common scale. The ionization mechanism itself is identified as quantum mechanical tunneling and the nature of the tunneling process is the direct origin of the scaling law.