hide
Free keywords:
Physics, Atomic Physics, physics.atom-ph, Condensed Matter, Quantum Gases, cond-mat.quant-gas, Physics, Chemical Physics, physics.chem-ph, Physics, Optics, physics.optics
Abstract:
A (diatomic) shape resonance is a metastable state of a pair of colliding
atoms quasi-bound by the centrifugal barrier imposed by the angular momentum
involved in the collision. The temporary trapping of the atoms' scattering
wavefunction corresponds to an enhanced atom pair density at low interatomic
separations. This leads to larger overlap of the wavefunctions involved in a
molecule formation process such as photoassociation, rendering the process more
efficient. However, for an ensemble of atoms, the atom pair density will only
be enhanced if the energy of the resonance comes close to the temperature of
the atomic ensemble. Herein we explore the possibility of controlling the
energy of a shape resonance by shifting it toward the temperature of atoms
confined in a trap. The shifts are imparted by the interaction of non-resonant
light with the anisotropic polarizability of the atom pair, which affects both
the centrifugal barrier and the pair's rotational and vibrational levels. We
find that at laser intensities of up to $5\times 10^{9}$ W/cm$^2$ the pair
density is increased by one order of magnitude for $^{87}$Rb atoms at $100
\mu$K and by two orders of magnitude for $^{88}$Sr atoms at $20 \mu$K.
