Calculations of collisions between cold alkaline-earth-metal atoms in a weak laser field

Abstract

We calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 50 atomic linewidths to the red of the 1 S0-1 P1 cooling transition. We evaluate loss rate coefficients due to both radiative and nonradiative state-changing mechanisms for temperatures at and below the Doppler cooling temperature. We solve the Schrödinger equation with a complex potential to represent spontaneous decay, but also give analytic models for various limits. Vibrational structure due to molecular photoassociation is present in the trap loss spectrum. Relatively broad structure due to absorption to the Mg2 1 Σu state occurs for detunings larger than about 10 atomic linewidths. Much sharper structure, especially evident at low temperature, occurs even at smaller detunings due to of Mg2 1 Πg absorption, which is weakly allowed due to relativistic retardation corrections to the forbidden dipole transition strength. We also perform model studies for the other alkaline earth species Ca, Sr, and Ba and for Yb, and find similar qualitative behavior as for Mg.34.50. Rk, 34.10.+x, 32.80.Pj

Line shapes of optical Feshbach resonances near the intercombination transition of bosonic ytterbium

“…(12) and (13) Γ A is the natural decay width of the atomic transition and λ A the wavelength of the atomic transition. The dimensionless rotational line strength factor for a transition from the ground scattering state to the excited 0 + u state in a bosonic isotope has the simple approximate form obtained by Machholm et al [38]:…”

“…To do this we have replaced in the effective potential, Eqs. (10) and (23), the standard term describing the resonance interaction −C (e) 3 /r 3 by the term in which retardation is taken into account: −(C (e) 3 /r 3 )[cos(r/λ) + (r/λ) sin(r/λ)], where λ = λ/(2π) [38,46]. The corrections to the binding energies caused by this change are listed in the column "Retardation 1" of Table III.…”

Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

“…Stable alkaline-earth isotopes with an even number of nucleons predominate, which therefore possess no nuclear magnetic moment: Their electronic spectra are free of hyperfine structure. This simplifies the interpretation of experimental data and facilitates comparison to theory [16]. The analysis of the photoassociative spectrum of cold 40 Ca atoms measured by Zinner et al may serve as an illustration [17].…”

Scattering length of the ground-stateMg+Mgcollision

“…The first experimental photoassociation spectra were reported for calcium [14] while photoassociation spectroscopy for alkaline earth atoms has been studied theoretically in Ref. [15] The coldest temperatures in dilute atomic gases are obtained by a process called evaporative cooling. Ground state collisions are crucial for evaporative cooling.…”