Emilio Mariotti

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.

Saturated absorption spectroscopy: Elimination of crossover resonances with the use of a nanocell

It is demonstrated that the velocity-selective optical pumping/saturation resonances of the reduced absorption in a Rb vapor nanocell with thickness L = λ, 2λ, and 3λ (resonant wavelength λ = 780 nm) allow for the complete elimination of crossover (CO) resonances. We observe well-pronounced resonances corresponding to the Fg = 3 → Fe = 2, 3, and 4 hyperfine transitions of the 85Rb D2 line with line widths close to the natural width. A small CO resonance located midway between Fg = 3 → Fe = 3 and Fg = 3 → Fe = 4 transitions appears only for L ≥ 4λ. The D2 line (λ = 852 nm) in a Cs nanocell exhibits a similar behavior. From the amplitude ratio of the CO and VSOP resonances, it is possible to determine the thickness of the column of alkali vapor in the range of 1–1000 μm. The absence of the CO resonances for nanocells with L ∼ λ is attractive for the frequency reference application and for studying the transitions between the Zeeman sublevels in external magnetic fields.

Light induced drift of sodium atoms in absence of wall adsorption

Abstract Experimental evidence of light induced drift of sodium atoms in absence of wall adsorption is here reported. The adsorption energy is reduced down to ∼ 0.1 eV by coating the cell with a thin and transparent film of silane which lowers the adsorption time to ∼ 10 -12 s and inhibits the formation of a sodium monolayer. The drift velocity is evaluated to be in agreement with the theoretical calculations.

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.

Accurate measurements of transition frequencies and isotope shifts of laser-trapped francium

An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by 1 order of magnitude. The deduced isotope shifts for 209-211Fr confirm the ISOLDE data. The frequency of the D2 transition of 212Fr--the accepted reference for all Fr isotope shifts--is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries.

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.

Giant modification of atomic transition probabilities induced by a magnetic field: forbidden transitions become predominant

The magnetic field-induced giant modification of probabilities for seven components of 6S1/2, Fg = 3 → 6P3/2, Fe = 5 transition of the Cs D2 line, forbidden by selection rules, is observed experimentally for the first time. For the case of excitation with circularly polarized laser radiation, the probability of a Fg = 3, mF = −3 → Fe = 5, mF = −2 transition becomes the largest of 25 transitions of the Fg = 3 → Fe = 2,3,4,5 group in a wide-range magnetic field of 200–3200 G. Moreover, the modification is the largest among D2 lines of alkali metals. A half-wave-thick cell (the length along the beam propagation axis L = 426 nm) filled with Cs has been used in order to achieve sub-Doppler resolution, which allows the large number of atomic transitions that appear in the absorption spectrum to be separated when an external magnetic field is applied. For B > 3000 G the group of seven transitions Fg = 3 → Fe = 5 is completely resolved and is located at the high frequency level of Fg= 3 → Fe = 2,3,4 transitions. The applied theoretical model describes very well the experimental curves.

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.