Standard electron sources have all energy spread above 0.3 eV. On the contrary, the initial electron energy dispersion obtained from a Magneto-Optical Trap for cold atoms, is in the 10 neV range. Thus, by ionizing cold atoms we expect to realize a bright and monoenergetic electron source. Based on an atomic beam, or on a standard 3D optical cooling, our cesium cold atom source is ionized either by a continuous or a pulsed laser. We study the behavior of the electron beam produced using time of flight or velocity imaging methods. The main idea is to combine this novel low energy highly monochromatic electron source with an Electron Controlled Chemical Lithography experiment and with 3D and energy resolved photoemission electron microscope (k-PEEM, from Mainz University, Germany). This unique combination should allow focusing monoenergetic (~1 meV) and very low electron energy (1-10 eV) down to unprecedented nanometer spots. The exclusive injection and diagnostic microscope, with such high spatial and energy resolution, will open the way towards controlled chemical reactions at the molecular level. During this presentation we will mainly explain the status of the experimental setup and details of the ionization process which involves electric field ionization of the excited cold atoms.

An extension of this work involves molecules. Indeed, cooling and trapping of molecules at ultracold temperatures (<1 mK) have been the most challenging tasks in experimental quantum physics for the last decade. A breakthrough in this field would give access to new quantum chemistry, studies of collective effects, metrology of fundamental constants, etc. Unfortunately, the successful laser cooling technique is rarely helpful in this context. Therefore, direct cooling of molecules is generally based on super-sonic expansion, cryogenic, or velocity filtering. All these methods suffer from the fact that they produce cold sample of molecules moving at velocities of couple of hundred meters per second. Thus, the problem to be solved is finding the way to stop molecules in the laboratory frame. Nowadays, many experiments use electromagnetic decelerators acting on the electric or magnetic permanent molecular dipole moment. Though successful, those methods have many drawbacks, such as high losses, cumbersome apparatus, etc. We have proposed a new approach that combines electrical charging of cooled neutral molecules, decelerating the resulting anions over short distances and, finally, removing the extra electron by photo-detachment. If such approach turns out to be successful, it will be a very important result for the cold molecule community. In medium-term perspective, we consider some “applications” of this method, such as violation parity measurement, creation of cold ion sources with the view of surface doping (NV centers in diamond, for example), etc.

Voditelji seminara IF-a: Nataša Vujičić i Damir Starešinić