Laser photoassociation

Essentially, an ultrashort laser pulse associates two colliding reactants to a new product. In the present case, a metastable excimer Hg2 is formed from two mercury atoms. This photoassociation process may be considered as the reverse of photodissociation. From a theoretical point of view, the important difference between processes (2) and (3) is that the unimolecular photodissociation (2) starts from bound states, whereas the bimolecular photoassociation (3) starts from continuum states, as demonstrated by model simulations in Fig. 1 (supported by Deutsche Forschungsgemeinschaft). 

Thorsheim HR, Weiner J, Julienne PS (1987) Laser-induced photoassociation of ultracold sodium atoms. Phys Rev Lett 58 2420-2423... 

Inoue G, Ku J K and Setser D W 1982 Photoassociative laser induced fluorescence of XeCI J.Chem.Phys. 76 733-4... 

Thorsheim H R, Weiner J and Juiienne P S 1987 Laser-induced photoassociation of ultracold sodium atoms Phys.Rev.Lett. 58 2420-3... 

For the photoassociation of the collision pair Na + Kr a crossed beam experiment was performed (Fig. 8.37). The Na-atoms were excited by a laser into the 3p state. These excited atoms collide with Kr-atoms. The collision pair was further excited by a second laser anticollinear with the first laser into a bound Rydberg state of the NaKr dimer which could decay by fluorescence into a bound A TJ state of the NaKr molecule [1099]. 

FIGURE 5.10 Two-color lambda-type photoassociation spectroscopy of Rb2- Colliding, trapped ultracold Rb atoms are irradiated by lasers of frequencies vj and V2- Spontaneous emission from the excited level at frequency leads to loss of the atoms from the trap. Optical-optical double-resonance signals (free-bound-bound) are observed when the frequency difference V2 — vj coincides with the binding energy of a lower-state vibrational level. (From Tsai, C.C. et al., Phys. Rev. Lett, 79,1245, 1997. With permission.)... 

The KRb experiments take place in a dual-species vapor-cell MOT [45]. Diode lasers at 767 and 780 nm are used to cool and trap K and Rb atoms, respectively, in the dark-spot MOT configuration. Atomic densities of 3 x lO cm" for K and 1 x 10 cm for Rb are realized, with corresponding temperatures of 300 and 100 tiK. Photoassociation is induced by illuminating the overlapping cold atomic clouds with light from a tunable cw titanium-sapphire laser (Coherent 899-29). This laser typically provides 500 mW with a linewidth of 1 MHz and its output is focused down to approximately match the size ( 300 p,m diameter) of the cold atom clouds. 

Band, Y.B. and Julienne, P.S., Ultracold-molecule production hy laser-cooled atom photoassociation, Phys. Rev. A, 51, R4317,1996. 

Photoassociation naturally lends itself to the resonant scattering treatment of a decaying resonance in Equation 6.22, which applies to the one-color case with position Ec = E —/jvi, strength aiigEol/) = r( , /)/(2i ),andshift8 (/).Thelattertwoare hnear in laser intensity I when I is low enough. Photoassociation is usually detected... 

T Prospects for Control of Ultracold Molecule Formation via Photoassociation with Chirped Laser Pulses... 

MODELING OF PHOTOASSOCIATION WITH CHIRPED LASER PULSES... 

Vatasescu, M. and Masnou-Seeuws, F., Time-dependent analysis of tunneling effect in the formation of ultracold molecules via photoassociation of laser-cooled atoms, Eur. Phys. J. D, 21, 191-204, 2002. 

Vala, J., Duheu, O., Masnou-Seeuws, F., Pillet, R, and Kosloff, R., Coherent control of cold-molecule formation through photoassociation using a chirped-pulsed-laser field,... 

Luc-Koenig, E., Kosloff, R., Masnou-Seeuws, F., and Vatasescu, M., Photoassociation of cold atoms with chirped laser pulses Time-dependent calculations and analysis of the adiabatic transfer within a two-state model, Phys. Rev. A, 70,033414, 2004. Luc-Koenig, E., Vatasescu, M., and Masnou-Seeuws, F., Optimizing the photoassociation of cold atoms by use of chirped laser pulses, Eur. Phys. J. D, 31, 239-262, 2004. 

Koch, C.P., Kosloff, R., Luc-Koenig, E., Masnou-Seeuws, R, and Crubellier, A., Short-pulse photoassociation with chirped laser pulses Calculation of the absolute number of molecules per pulse, J. Phys. B Atom. Mol. Opt. Phys., 39, S1017-S1041, 2006. 

Adiabatic Raman Photoassociation with Shaped Laser Pulses... 

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