A. Crubellier

Experimental versus theoretical rates for photoassociation and for formation of ultracold molecules

We report on the spectra of the long-range attractive molecular states of the Cs/sub 2/ dimer below the dissociation limits 6s+6p/sub 1/2/ and 6s+6p/sub 3/2/ which are accessible by molecular photoassociation of cold Cs atoms. For the states O/sub u//sup +/ and O/sub g//sup -/(6s+6p/sub 3/2/), we have performed trap-loss measurements, which are in good agreement with the theoretical calculations, performed in a perturbative approach. For the O/sub g//sup -/ and 1/sub u/(6s+6p/sub 3/2/) states, we observe, after spontaneous decay of the electronically excited molecules, the formation of translationally cold molecules. A rate of formation of cold molecules of the order of /spl sim/10/sup 6/ molecules per second is obtained in the case of the state O/sub g//sup

Photoassociation in a gas of cold alkali atoms: I. Perturbative quantum approach

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Measurement of the three-photon detachment cross sections of the negative ions of iodine, bromine and fluorine at the wavelength 1.0642 mu m

We develop a quantum-mechanical approach to the photoassociation phenomenon in a sample of cold atoms initially at thermal equilibrium with temperature T. We calculate the rate of formation of molecules in the weak field regime using a perturbative approach. Analytical expressions are obtained for the overlap between the initial and final molecular wavefunctions, and are shown to agree with numerical calculations. The photoassociation rate is found to decrease with increasing atomic mass m, from Li to Cs. Also considered is the heating of the atomic sample through spontaneous photodissociation.

Feshbach resonance in d -wave collisions

The three-photon detachment cross sections of the ions F-, Br- and I- are measured, using the fundamental 1064.2 nm wavelength of a single-mode Nd:YAG laser. The detachment signal is measured by detecting the neutral atoms produced from an ionic beam of kinetic energy 1.2 keV. The data analysis takes into account the laser pulse time profile, the actual spatial profile of the laser beam in the interaction region, and the fast motion of the ions through the laser beam during the laser pulse. Saturation of the three-photon process is observed and used to normalise the detachment signal. The authors obtain sigma (F-)=6.1

Formation of cold Cs2 molecules through photoassociation

+2.6-1.8*10-95 s2 m6, sigma (Br-)=1.6+0.8-0.6*10-94 m6 and sigma (I-)=3.3+16-1.1*10-94 s2 m6. These measured cross sections are compared with theoretical predictions. The result obtained on F- agrees with a very recent measurement performed with a different technique.

Threshold effects in the photoassociation of cold atoms: R−6 model in the Milne formalism

We analyse a narrow Feshbach resonance with ultra-cold chromium atoms colliding in d-wave. The resonance is made possible by dipole-dipole interactions, which couple an incoming

Three-Photon Detachment of Iodine Negative Ions

l=2

Oscillations in superradiance with long-duration pumping pulses.

collision channel with a bound molecular state with

Experimental evidence for collision-induced superradiance

l=0

Photoassociative molecular spectroscopy for atomic radiative lifetimes

. We find that three-body losses associated to this resonance increase with temperature, and that the loss feature width as a function of magnetic field also increases linearly with temperature. The analysis of our experimental data shows that the Feshbach coupling is small compared both to the temperature and to the density limited lifetime of the resonant bound molecular state. One consequence is that the three body losse rate is proportionnal to the square of the number of atoms, and that we can directly relate the amplitude of the losses to the Feshbach coupling parameter. We compare our measurement to a calculation of the coupling between the collisionnal channel and the molecular bound state by dipole-dipole interactions, and find a good agreement, with no adjustable parameter. An analysis of the loss lineshape is also performed, which enables to precisely measure the position of the resonance.