Paola Bicchi

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.

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.

Ultrafine particle formation by resonant laser excitation of potassium molecules

Abstract In a heat pipe oven containing potassium and a noble gas we have observed a large production of metallic potassium particles upon resonant laser excitation of the K2 molecules. This is a new method for particle production, based on the strong local heating of the vapor due to the high absorption rate of the laser light. As a consequence of the disequilibrium caused at the gas/vapour boundary by this heating, a supersaturated region is created where the vapor condenses and produces ultrafine particles.

Rosonant laser excitation of potassium vapour: Experimental investigation of energy-pooling collisions and plasma production

SummaryThe illumination of potassium vapour by means of a c.w. dye-laser resonant with the fundamental 4S→4P transitions results in the excitation of high-lying atomic and molecular states. In the present paper we report a spectroscopic study of this phenomenon and experimental evidence that the mechanisms responsible for the population of some of the levels not directly excited by the laser involve the creation of a plasma in the vapour.RiassuntoQuando vapori di potassio sono illuminati dalla luce di un laser a colorante risonante con la transizione fondamentale 4S→4P, si osservano transizioni sia da livelli atomici molto alti, sia dalivelli molecolari. In questo articolo si descrive uno studio spettroscopico di questi fenomeni e si dà la prova sperimentale che il meccanismo responsabile della popolazione di alcuni dei livelli non direttamente eccitati dal laser richiede la creazione di un plasma nel vapore.РезюмеОбпучение паров калия лазером на красителях с основными переходами 4S→4P приводит к возбуждению высоколежащих атомных и молекулярных состояний. В этой работе мы сообщаем резулбтаты спектроскопических исследований этого явления и экспериментальное подтверждение, что механизм, ответственный за заселение некоторых уровней, в результате не прямого возбуждения лазером, включает образование плазмы в паре.

Observation of fluorescence from high-lying states of potassium in a sodium-potassium mixture upon resonant laser excitation

Abstract Fluorescence from three of the highly excited states of K (6S, 5P, and 4D) has been observed in a mixed vapour of sodium and potassium upon irradiation of two cw dye lasers tuned to the D resonance lines of sodium and potassium. Processes that may populate these levels via K ∗ (4P) + Na ∗ (3P) collisions are discussed.

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.

Radiation trapping and vapor density of indium confined in quartz cells

Abstract We have measured, in the 700–950°C temperature range, the effective lifetime of the 6S 1 2 excited level of indium vapor confined in quartz cells. The self trapping results much lower than expected suggest an effective vapor density lower than the one calculated at the thermal equilibrium. A possible explanation of this large deviation has been found in the increasing adsorption rate of indium at the cell walls. Partial fluorescence spectrum of the adsorbed atoms is reported.

Energy pooling collision cross section measurements in indium: the In(6S1/2)+In(6S1/2) to In(nP)+In(5P3/2) process

The quantitative investigation of the energy pooling collision (EPC) process between resonantly laser excited In atoms is reported. The process is studied in a laser induced fluorescence (LIF) experiment where the nP populations, with n=11, 10 and 9, are monitored. The population mechanism for these levels is verified via a temporal analysis of the fluorescence signals. This is possible in In due to the strongly reduced self trapping of the resonant radiation. The cross section for energy pooling collision to these nP levels has been derived by considering the Rydberg character of these levels.

Observation of the reflection of laser oriented atoms by non disorienting surfaces

Abstract Experimental evidence of the reflection of oriented Na atoms on the walls of a cell coated with silanes is reported. The detection method is based on the optical activity of an oriented vapour.