Optics Seminar

In a first part, the orientation of a beam of ammonia molecules produced by a buffer gas cell and guided through an electrostatic quadrupole will be established. Ammonia molecules are injected in a cryogenically-cooled gas cell in which they get collisionally cooled by helium to a temperature of 5 – 15 K. The internally cold ammonia molecules are then guided through a 2.15 m long electrostatic quadrupole guide made with three 90° bends [1]. Internally and translationally cold ammonia is then probed using (2+1) resonance-enhanced multiphoton ionisation (REMPI) with different light polarisations. The relative rotational state populations are determined by fitting our results with Monte-Carlo simulations and PGOPHER, with the orientation of ammonia subsequently determined. Different electric field regions of the experiment influence the ammonia orientation and a new design of the experiment is predicted to have control over 95 % of the guided ammonia orientation [2]. The experiment has recently been updated accordingly, and experiments are in progress to control and probe the ammonia orientation in our new set-up.In a second part, I will describe recent results from an on-going experiment involving radicals transmitted through a magnetic guide consisting of four Halbach arrays and two skimming blades [3]. Previous studies showed that the magnetic guide can purify a beam coming from a Zeeman decelerator and successfully guide hydrogen atoms with a tuneable velocity between 125 and 250 ms-1 [4]. New experiments are examining whether the magnetic guide can act as a stand-alone beam filter, transmitting only those particles travelling within the target velocity range from an effusive source.