Parity nonconservation that originates from the weak interaction of atomic electrons with the nuclei in heliumlike gadolinium and europium is considered. An experiment with a polarized ion beam is discussed. The mixed hyperfine-and weak-quenching effect in Gd 62ϩ and Eu 61ϩ isotopes is shown to lead to an asymmetry of the photon emission relative to the ion beam polarization. With complete beam polarization, the magnitude of the asymmetry in photon counting rates reaches about 0.39ϫ10 Ϫ3 in gadolinium and is about 0.11ϫ10 Ϫ3 in europium.

The influence of nuclear polarization on the bound-electron g factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K-and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron g factor in highly charged ions. PACS number(s): 12.20. Ds, 31.30.Jv, 32.10.Dk Typeset using REVT E X 1

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We investigate the double K-shell ionization of heliumlike ions caused by the absorption of a single photon with energies being much smaller than the rest energy of an electron. In the near-threshold region, differential and total cross sections of the process are calculated for light ions, taking into account the leading orders of the 1/Z and ␣Z expansions. QED perturbation theory with respect to the parameter 1/Z exhibits a fast convergence in the entire nonrelativistic domain for moderate nuclear charge numbers Zу2. Going beyond the electric dipole approximation leads to a forward/backward asymmetry in the angular distributions for the ejected electrons with respect to the incident photon beam. A comparison of theoretical predictions for the ratio of double-to-single photoionization cross sections with available experimental data for a number of neutral atoms is also presented.

Despite the dangers associated with tropical cyclones and their rainfall, the origins of storm moisture remains unclear. Existing studies have focused on the region 40-400 km from the cyclone center. It is known that the rainfall within this area cannot be explained by local processes alone but requires imported moisture. Nonetheless, the dynamics of this imported moisture appears unknown. Here, considering a region up to three thousand kilometers from storm center, we analyze precipitation, atmospheric moisture and movement velocities for North Atlantic hurricanes. Our findings indicate that even over such large areas a hurricane's rainfall cannot be accounted for by concurrent evaporation. We propose instead that a hurricane consumes pre-existing atmospheric water vapor as it moves. The propagation velocity of the cyclone, i.e. the difference between its movement velocity and the mean velocity of the surrounding air (steering flow), determines the water vapor budget. Water vapor available to the hurricane through its movement makes the hurricane self-sufficient at about 700 km from the hurricane center obviating the need to concentrate moisture from greater distances. Such hurricanes leave a dry wake, whereby rainfall is suppressed by up to 40% compared to its long-term mean. The inner radius of this dry footprint approximately coincides with the radius of hurricane self-sufficiency with respect to water vapor. We discuss how Carnot efficiency considerations do not constrain the power of such open systems that deplete the pre-existing moisture. Our findings emphasize the incompletely understood role and importance of atmospheric moisture supplies, condensation and precipitation in hurricane dynamics.

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A calculation of the simplest part of the second-order electron self-energy (loop after loop irreducible contribution) for hydrogen-like ions with nuclear charge numbers 3 ≤ Z ≤ 92 is presented. This serves as a test for the more complicated second-order self-energy parts (loop inside loop and crossed loop contributions) for heavy one-electron ions. Our results are in strong disagreement with recent calculations of Mallampalli and Sapirstein for low Z values but are compatible with the two known terms of the analytical Zαexpansion.

Precipitation generates small-scale turbulent air flows the energy of which ultimately dissipates to heat. The power of this process has previously been estimated to be around 2-4 W m −2 in the tropics: a value comparable in magnitude to the dynamic power of the global circulation. Here we suggest that this previous power estimate is approximately double the true figure. Our result reflects a revised evaluation of the mean precipitation path length H P . We investigate the dependence of H P on surface temperature, relative humidity, temperature lapse rate and degree of condensation in the ascending air. We find that the degree of condensation, defined as the relative change of the saturated water vapor mixing ratio in the region of condensation, is a major factor determining H P . We estimate from theory that the mean large-scale rate of frictional dissipation associated with total precipitation in the tropics lies between 1 and 2 W m −2 and show that our estimate is supported by empirical evidence. We show that under terrestrial conditions frictional dissipation constitutes a minor fraction of the dynamic power of condensation-induced atmospheric circulation, which is estimated to be at least 2.5 times larger. However, because H P increases with surface temperature T s , the rate of frictional dissipation would exceed that of condensation-induced dynamics, and thus block major circulation, at T s 320 K in a moist adiabatic atmosphere.