50 research outputs found
Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms
We report Monte Carlo wave function simulation results on cold collisions
between magnesium atoms in a strong red-detuned laser field. This is the normal
situation e.g. in magneto-optical traps (MOT). The Doppler limit heating rate
due to radiative collisions is calculated for Mg-24 atoms in a magneto-optical
trap based on the singlet S_0 - singlet P_1 atomic laser cooling transition. We
find that radiative heating does not seem to affect the Doppler limit in this
case. We also describe a channelling mechanism due to the missing Q branch in
the excitation scheme, which could lead to a suppression of inelastic
collisions, and find that this mechanism is not present in our simulation
results due to the multistate character of the excitation process.Comment: 4 pages, RevTeX 4; v2 contains minor revisions based on referee
comments (5 pages
Scattering length of the ground state Mg+Mg collision
We have constructed the X 1SIGMAg+ potential for the collision between two
ground state Mg atoms and analyzed the effect of uncertainties in the shape of
the potential on scattering properties at ultra-cold temperatures. This
potential reproduces the experimental term values to 0.2 inverse cm and has a
scattering length of +1.4(5) nm where the error is prodominantly due to the
uncertainty in the dissociation energy and the C6 dispersion coefficient. A
positive sign of the scattering length suggests that a Bose-Einstein condensate
of ground state Mg atoms is stable.Comment: 15 pages, 3 figures, Submitted Phys. Rev.
Theoretical study of the
Excitation spectra arising from
and electronic transitions in the Cd-rare
gas (RG) van der Waals molecules are calculated using newly
obtained theoretical potential curves for these species. In the
molecular structure calculations, Cd20+ and RG8+ cores are
simulated by energy-consistent pseudopotentials which also account
for scalar-relativistic effects and spin-orbit (SO) interaction
within the valence shell. Potential energies in the
coupling scheme have been obtained by means of ab initio
complete-active-space multiconfiguration self consistent-field
(CASSCF)/complete-active-space multireference second-order
perturbation theory (CASPT2) calculations with a total 28 correlated
electrons, while the SO matrix has been computed in a reduced CI
space restricted to the CASSCF level. The final Ω potential
curves are obtained by diagonalization of the modified SO matrix
(its diagonal elements before diagonalization substituted for the
corresponding CASPT2 eigen-energies). The spectroscopic parameters
for the ground and several excited states of the Cd-RG complexes
deduced from the calculated potential curves are in quite reasonable
agreement with available experimental data. In addition, the radial
Schrödinger equation for nuclear motion was solved numerically
with the calculated potentials to evaluate the corresponding
vibrational levels and radial wavefunctions. The latter have been
used in the calculation of the appropriate Franck-Condon factors to
yield information on relative intensities of the vibrational bands
of the Cd-RG complexes. The theoretical vibrational progressions are
discussed in the context of experimental spectra