12,470 research outputs found
Ionization of atoms by few-cycle EUV laser pulses: carrier-envelope phase dependence of the intra-pulse interference effects
We have investigated the ionization of the H atom by intense few-cycle laser
pulses, in particular the intra-pulse interference effects, and their
dependence on the carrier-envelope phase (CEP) of the laser pulse. In the final
momentum distribution of the continuum electrons the imprint of two types of
intra-pulse interference effects can be observed, namely the temporal and
spatial interference. During the spatial interference electronic wave packets
emitted at the same time, but following different paths interfere leading to an
interference pattern measurable in the electron spectra. This can be also
interpreted as the interference between a direct and a scattered wave, and the
spatial interference pattern as the holographic mapping (HM) of the target.
This HM pattern is strongly influenced by the carrier-envelope phase through
the shape of the laser pulse. Here, we have studied how the shape of the HM
pattern is modified by the CEP, and we have found an optimal CEP for the
observation of HM
Precursors of an upcoming solar cycle at high latitudes from coronal green line data
After reviewing potential early indicators of an upcoming solar cycle at high
latitudes, we focus attention on the rush-to-the-poles (RTTP) phenomenon in
coronal green line emission. Considering various correlations between
properties of the RTTP with the upcoming solar cycle we find a correlation
between the rate of the RTTP and the time delay until the maximum of the next
solar cycle. On the basis of this correlation and the known internal
regularities of the sunspot number series we predict that, following a minimum
in 2019, cycle 25 will peak in late 2024 at an amplitude of about 130 (in terms
of smoothed monthly revised sunspot numbers). This slightly exceeds the
amplitude of cycle 24 but it would still make cycle 25 a fairly weak cycle.Comment: 17 pages, 5 figures J. Atm. Sol.-Terr. Phys., in pres
Stable and habitable systems with two giant planets
We have studied planetary systems which are similar to the Solar System and
built up from three inner rocky planets (Venus, Earth, Mars) and two outer gas
giants. The stability of the orbits of the inner planets is discussed in the
cases of different masses of the gas planets. To demonstrate the results
stability maps were made and it was found that Jupiter could be four times and
Saturn could be three times more massive while the orbits of the inner planets
stay stable. Similar calculations were made by changing the mass of the Sun. In
this case the position of the rocky planets and the extension of the liquid
water habitable and the UV habitable zones were studied for different masses of
the Sun. It was found that the orbits of the planets were stable for values
greater than 0.33 M_Sun where M_Sun is the mass of the Sun and at lower masses
of the Sun (at about 0.8 M_Sun) only Venus, but for higher mass values (at
about 1.2 M_Sun) Earth and also Mars are located in both habitable zones.Comment: 8 page
Investigation of the composition of the Luna 16 lunar sample
The concentrations of aluminum, manganese, sodium, chromium, iron, cobalt, and 12 rare earth elements were determined by neutron activation analysis using slow neutrons. Oxygen and silicon were determined using a fast neutron generator. Mossbauer spectroscopy was used to investigate iron compounds in Luna 16 regolith samples from the upper part of the core
Ionization of helium by slow antiproton impact: total and differential cross sections
We theoretically investigate the single and double ionization of the He atom
by antiproton impact for projectile energies ranging from ~keV up to
~keV. We obtain accurate total cross sections by directly solving the
fully correlated two-electron time-dependent Schr\"odinger equation and by
performing classical trajectory Monte-Carlo calculations. The obtained
quantum-mechanical results are in excellent agreement with the available
experimental data. Along with the total cross sections, we also present the
first fully \textit{ab initio} doubly differential data for single ionization
at 10 and 100~keV impact energies. In these differential cross sections we
identify the binary-encounter peak along with the anticusp minimum.
Furthermore, we also point out the importance of the post-collisional
electron-projectile interaction at low antiproton energies which significantly
suppresses electron emission in the forward direction
Semiclassical model for calculating fully differential ionization cross sections of the H molecule
Fully differential cross sections are calculated for the ionization of H
by fast charged projectiles using a semiclassical model developed previously
for the ionization of atoms. The method is tested in case of 4 keV electron and
6 MeV proton projectiles. The obtained results show good agreement with the
available experimental data. Interference effects due to the two-center
character of the target are also observed and analyzed.Comment: 11 pages, 4 figure
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