Buffer-gas Loading and Magnetic Trapping of Molecules

Abstract

Ultracold and cold molecules have enormous potential for yielding a wealth of new physics and new technologies. Molecules possess several features that greatly increase the possibilities for new interactions, collective quantum states and effects, collisional processes, fundamental symmetry tests and chemical processes. This is due to 1) the strong interactions between the dipole moments of polar molecules, 2) the rotational and vibrational internal structure of all molecules, and 3) the easily orientable internal electric field of many molecules. The promise of cold and ultracold molecules will only be realized when samples can be prepared with at least the same ease in which we now prepare atomic samples. Several approaches towards trapping of molecules, the key first step toward studying ultracold molecules at high density, have already succeeded: direct cooling of molecules via a buffer gas, mechanical slowing of a pulsed molecular beam with electric fields and photoassociation of alkali atoms. In the ICAP 2002 session on molecules I described some of the current theoretical results and predictions about ultracold molecular systems. Profs. Meijer and Heinzen described results on pulsed beam slowing and photoassociation. This contribution describes some of the key results on buffer-gas loading of molecules. . The challenge in molecular physics is to achieve with molecules what has so far been limited to atoms. This prospect is perhaps even more appealing, since molecules offer a vast range of properties not available with atoms. Unlike atoms, molecules are generally non-spherical and have rotational and vibrational degrees of freedom. Apart from that, molecules possess both even and odd multipole moments -electric and magnetic -that are all coupled to the rotating molecular frame. As a result, any molecular interaction, whether with other molecules or with external fields, is shaped and refined by a transformation between the rotating molecular frame and the space-fixed laboratory frame.Cooling and trapping of molecules can produce a number of significant benefits for a wide variety of applications. Availability of reduced line broadening and long interaction times can benefit precision spectroscopy [8], and coherent control [9]. Cooling of internal molecular states, combined with long interaction times, can greatly increase the sensitivity of certain precision measurements [10]. Low translational energy of the cooled molecules will facilitate external-field manipulations of molecular trajectories and orientations [11]-[13]. In the regime where the deBroglie wavelength exceeds molecular dimensions, reactive collisions start exhibiting significant quantum effects [14]. Reactive and non-reactive collisions of ultracold molecules are of significant interest [15], [16]. Beyond collisional properties, proposals exist for employing electric dipoles of ultracold molecules to implement quantum computing [17]. Finally, achiev-