4,770 research outputs found
Calculation of isotope shifts and relativistic shifts in CI, CII, CIII and CIV
We present an accurate ab initio method of calculating isotope shifts and
relativistic shifts in atomic spectra. We test the method on neutral carbon and
three carbon ions. The relativistic shift of carbon lines may allow them to be
included in analyses of quasar absorption spectra that seek to measure possible
variations in the fine structure constant, alpha, over the lifetime of the
Universe. Carbon isotope shifts can be used to measure isotope abundances in
gas clouds: isotope abundances are potentially an important source of
systematic error in the alpha-variation studies. These abundances are also
needed to study nuclear reactions in stars and supernovae, and test models of
chemical evolution of the Universe
Fermi acceleration in time-dependent rectangular billiards due to multiple passages through resonances
We consider a slowly rotating rectangular billiard with moving boundaries and
use the canonical perturbation theory to describe the dynamics of a billiard
particle. In the process of slow evolution certain resonance conditions can be
satisfied. Correspondingly, phenomena of scattering on a resonance and capture
into a resonance happen in the system. These phenomena lead to destruction of
adiabatic invariance and to unlimited acceleration of the particle.Comment: 20 pages. Presented on School-Conference "Mathematics and Physics of
Billiard-Like Systems" (Ubatuba, 2011). Accepted to Chao
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