Slowing and Speeding Molecular Beams by Means of a Rapidly Rotating Source

Abstract

Mounting a molecular beam source near the tip of a hollow high-speed rotor provides a means to shift the velocity distribution of the beam downward or upward over a wide range. We describe the construction of such a device and experiments and model calculations characterizing its operation, for both supersonic and effusive beams of rare gases, O 2 , CH 3 F, and SF 6 . For example, the flow velocity of a rotating supersonic beam of O 2 was accelerated to above 1000 m/s (corresponding to a kinetic energy of 2200 K and deBroglie wavelength of 0.1 Å) and decelerated (when seeded in Xe) to below 70 m/s (corresponding to a kinetic energy below 10 K and deBroglie wavelength of nearly 2 Å). With improvements in prospect, the rotating beam source offers a versatile and relatively simple way to enhance techniques for manipulating molecular trajectories. † Part of the special issue "Harold Johnston Festschrift".

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

“…43 Other direct techniques such as collisional cooling 44 and rotating nozzle slowing and velocity filtering have been implemented. [45][46][47] An optical Stark deceleration scheme utilizing optical dipole forces induced by pulsed fields has also been demonstrated. 48 Rempe's group 49,50 has applied an optoelectrical method for cooling and collecting polar molecules in an electric trap.…”

High-Flux Beam Source for Cold, Slow Atoms or Molecules

“…), significant effort has been put into developing improved atomic beam sources [1][2][3][4][5][6][7]. Work on developing cold molecular sources has recently been a particularly active field of research [8][9][10][11][12][13]. As with atoms, one of the aims is to produce quantum degenerate gases, including those comprising strongly interacting electric dipoles [14 -16].…”

Micro-Kelvin cold molecules.

“…For experiments where the thermal rotational state distribution of the molecules presents a problem, using this technique in conjunction with other molecular beam cooling techniques such as the counter-rotating nozzle [10] has promise to create samples of cold molecules in an experimentally simple and low cost apparatus. It should be noted that in this discussion we have neglected the effects of inelastic collisions with either ground or electronically excited 87 Rb on the density of cold molecules that can be formed.…”

“…One conceptually straightforward technique for slowing down molecules in a supersonic beam is to move the molecular beam valve backwards in the laboratory reference frame with a velocity equal and opposite to that of the escaping molecular beam, canceling out the translational velocity in the laboratory frame [10]. Other techniques fall broadly into three categories: using external electric or magnetic fields using optical fields or using collisions.…”