Carmela Marinelli

Light Induced Atom Desorption

In the present paper we report experimental evidence of a new effect, observed for the first time by Gozzini et al. on sodium vapour, in which an important rubidium vapour density increase (larger than one order of magnitude) is observed when silane-coated cells are shined by non-resonant and weak light. The effect is due to non-thermal light-induced atom desorption. A preliminary analysis of its dependence on the light power density and on the wavelength has been carried out.

Atom cooling by White light

The performances of white light cooling are shortly reviewed and discussed. The velocity distributions modified by the cooling laser are calculated under different boundary conditions and a new experimental approach, which permits to obtain a sharp edge laser bandwidth, is taken into consideration. Finally, the preliminary experimental results on a sodium beam cooled by a lamp laser are reported.

Full control of sodium vapor density in siloxane-coated cells using blue LED light-induced atomic desorption

We propose and experimentally implement a method, based on light-induced atomic desorption, for controlled generation of large sodium densities in siloxane-coated cells, kept at room temperature. An array of blue LEDs is used to desorb sodium atoms from the cell walls. The required atomic vapor density is achieved and stabilized by controlling the LED power through the feedback given by the sodium fluorescence. We show that sodium densities corresponding to about 400 K can be obtained and kept stable for a long time with less than 6 mW of LED light power. Moreover, this technique allows for precise vapor density modulation with a frequency of tenths of hertz, which is not possible using traditional heating methods.

Optical recording in Rb loaded-porous glass by reversible photoinduced phase transformations

We report reversible phase transformations in Rb loaded-porous glass irradiated with weak laser light which allow us to realize image storage on it. The effect is due to photo-induced changes of Rb distribution inside the glass pores, where atomic photodetachment and confinement produce either formation or evaporation of Rb nanoclusters. These processes depend on light frequency and intensity making controllable by light the porous glass transparency. We demonstrate that porous glass doped with Rb can be used as a support to record a light pulse for a long time as well as to remember the order of light colors in an illumination sequence.

A 670 nm external-cavity single mode diode laser continuously tunable over 18 GHz range

Abstract It is demonstrated that a 670 nm visible diode laser, operating in external cavity and without any additional anti-reflection coating treatment on the output facet, can perfectly operate in a single mode regime and can be continuously tuned over a frequency range larger than 18 GHz. The external cavity is closed by a grating and it does not need etalons or other frequency selective devices. The very wide single mode scanning has been obtained by a servo system which locks the internal laser solitary cavity to the external one that is supported by three quartz bars. An example of a linear single frequency scanning is reported where the absorption spectrum corresponding to the 2S→2P transition of 7 Li is shown.

Dynamics of rubidium light-induced atom desorption (LIAD)

Abstract Rubidium desorption induced by weak and non-resonant light has been observed in silane coated cells. The effect is non-thermal and produces a huge variation of the vapor density at room temperature. This effect has been observed, for the first time, by Gozzini et al. with sodium upon similar conditions. The dynamics of this new effect is here discussed and the desorption-adsorption rates are measured.

Light-induced atomic desorption and related phenomena

We review some recent studies on light-induced atomic desorption (LIAD) from dielectric surfaces. Alkali-metal atoms adsorbed either on organic films or on porous glass are released into the vapor phase under illumination. The measurements were performed in Pyrex resonance cells either coated with siloxane films or containing a porous glass sample. In both cases, the experimental results show that LIAD can be used to produce atomic densities suitable for most atomic physics experiments. Moreover, we find that photoinduced effects, correlated with LIAD, produce reversible formation and evaporation of alkali-metal clusters in porous glass. These processes depend on the light frequency, making the porous glass transmittance controllable by light.

Light desorption from an yttrium neutralizer for Rb and Fr magneto-optical trap loading

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with (85)Rb, the first demonstration of the photodesorption-aided loading of a (210)Fr MOT is shown.

Francium trapping at the INFN-LNL facility

A brief review of the Francium trapping experiments at the INFN-LNL facility is presented in the wide context of Atomic Parity-Nonconservation (APNC), which, as long as acquiring more precise and new spectroscopic data on the Francium isotopes, is the ultimate goal of the experiment. Due to its instability, Francium atoms must be produced continuously by a nuclear fusion–evaporation reaction into a heated Gold target hit by a beam of accelerated oxygen ions. Francium is then extracted in the ionic form and guided by an electrostatic line to the actual science chamber, where the ions are neutralized. Atoms are then cooled down and trapped in a Magneto-Optical Trap (MOT) to ensure both the availability of a sufficiently populated and stable atomic sample and to eliminate the Doppler broadening which would affect the precision of the measurements. A review of the recent improvements to the experimental apparatus and to the detection techniques that led to a sensitivity better than five atoms is presented. The final part of this paper deals with a summary of the recent results obtained by our collaboration and a short outlook for the immediate future.

An efficient photo-atom source

Abstract We show that it is possible to obtain a very efficient photo-atom source, whose atom flux is regulated by light. The atom release is due to the recently observed light-induced atom desorption effect from silane coated cells. We report the results obtained at room temperature with rubidium in a double body cell coated with (poly)dimethyl-siloxane. This kind of photo-atom source can be immediately extended to other alkali atoms, namely sodium, potassium and cesium. Possible applications are discussed.