Pure-state molecular beams: Production of rotationally, vibrationally, and translationally selected CsF beams

Publisher Website
Google Scholar
Abstract
Beams of CsF in selected vibrational (v=0,1,2,3,4) and rotational (J,M=1,0) states, with narrow velocity distributions, have been produced via an improved microwave molecular beam electric resonance (MBER) method utilizing ’’displacement focusing.’’ The apparatus consists of an effusive graphite oven source, a slotted‐disk velocity selector, and two electrostatic quadrupole fields. The first field focuses the (J,M) = (2,0) state through an off‐axis collimating orifice into a microwave cavity. Here microwave radiation stimulates the J=2→1 transition for a specified v state. Then a second (’’refocusing’’) quadrupole delivers the specified (v,J,M) = (v,1,0) state to an image point (a collimated surface ionization mass filter detector). The final focused and state‐selected beam, say (0,1,0), has a purity ≳95% with respect to J,M. However, the best over‐all (v,J,M) state purity achieved was 83% (0,1,0), with 17% of ’’background’’ [of which 4% is actually (0,1,0), 4% is (1,1,0), 4% (v,1,0) with v?2, and the remaining 5% unselected (scattered) CsF]. Using the present effusive oven source, the best intensity achieved for a state‐selected (0,1,0) beam (of velocity 3.65×104 cm sec−1) was 1×105 molecule sec−1, corresponding to a flux density of 1.3×109 molecule cm−2 sec−1.