Efficiency of photodesorption of Rb atoms collected on polymer organic film in vapor-cell

The efficiency of photodesorption of Rb atoms previously collected on polymer organic film has been studied in detail. This study was carried out in a Pyrex glass cell of which the inner surface was covered with (poly)dimethylsiloxane (PDMS) film and illuminated by a powerful flash lamp. The desorption dynamic of the Rb atoms density in the cell caused by the illumination and percentage of desorbed atoms was studied by using of Rb resonance lamp and free running diode laser as sources of probing light. It was determined that 85 percent collected chemical active Rb atoms and stored during 16 s in the closed cell, 75 percent in the pumped cell can be desorbed by single flash of the lamp. The number of stored atoms decays with a characteristic time of 60 min in isolated cell and with a time 12.4 min in a pumped cell. We believe that this efficient method of collection and fast realization of atoms or molecules could be used for enhancement of sensitivity of existed sensors for the trace detection of various elements (including toxic or radioactive ones) which is important to environmental applications, medicine or in geology. The effect might help to construct an efficient light-driven atomic source for a magneto-optical trap in a case of extremely low vapor density or very weak flux of atoms, such as artificial radioactive alkali atoms.     

The Legnaro Francium Magneto-Optical Trap

Hyperfine Interactions - Laser cooling and trapping of radioactive atoms represent the new frontier in atomic physics and a new powerful tool in nuclear physics. We are setting up at the...     

A Monte Carlo simulation of a stroboscopic laser diagnostics of ordered ion beams in a storage ring

A Monte Carlo code combined with a particle tracking program has been used to study a stroboscopic laser diagnostic system that is able to detect a string-like ordered ion beam. Different ion species have been studied to evaluate the diagnostics capability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Francium sources and traps for fundamental interaction studies

Francium is one of the best candidates for atomic parity nonconservation (APNC) and for the search of permanent electric dipole moments (EDMs). APNC measurements test the weak force between electrons and nucleons at very low momentum transfers. They also represent a unique way to detect weak nucleon-nucleon interactions. EDMs are instead related to the time-reversal symmetry. Preliminary to these fundamental measurements are precision studies in atomic spectroscopy and the development of magneto-optical traps (MOT), which partially compensate for the lack of stable Fr isotopes. At LNL Legnaro, francium is produced by fusion of 100-MeV ¹⁸O with ¹⁹⁷Au in a thick target, followed by evaporation of neutrons from the compound nucleus. Francium diffuses inside the hot target (1200 K) and is surface ionized for injection at 3 keV in an electrostatic beamline. Typically, we produce 1×10⁶ (²¹⁰Fr ions)/s for a primary flux of 1.5×10¹² particles/s. We have studied Fr yields as a function of primary beam energy, intensity, and target temperature. Information on the efficiency of bulk diffusion, surface desorption and ionization is deduced. The beam then enters a Dryfilm-coated cell, where it is neutralized on a heated yttrium plate. The escape time of neutral Fr (diffusion + desorption) is approximately 20 s at 950 K, as measured with a dedicated setup. In the MOT, we use 6 orthogonal Ti:sapphire laser beams for the main pumping transition and 6 beams from a stabilized diode repumper. Fluorescence from trapped atoms is observed with a cooled CCD camera, in order to reach noise levels from stray light equivalent to approximately 50 atoms. Systematic tests are being done to improve the trapping efficiency. We plan to further develop Fr traps at LNL; in parallel, we will study APNC and EDM techniques and systematics with stable alkalis at Pisa, Siena, and Ferrara.     

Estimation of the Error of the Interference Method for Determining the Dielectric Permittivity on the Example of Transformer Oil in the Ka-Band

Radiophysics and Quantum Electronics - We estimate the error of the previously proposed method for determining the dielectric permittivity of liquids on the basis of the interference dependence of...     

Light-induced drift of neon under optical excitation from a metastable state

A running light wave, resonant with the neon transition 1s₅-2p₂, has been found out to affect the spatial distribution of neon atoms in a positive discharge column. The effect has shown an antisymmetric dependence (typical of the light-induced drift) on the tuning out of the radiation frequency relatively the absorption line centre, as well as on the direction of the light wave vector.     

Sharp edge broad-band lasers for "white-light" cooling in storage rings

We have developed broad-band laser sources which show a sharp edge in their spectra and are particularly suitable for ``white-laser' cooling of ions in storage rings. They allow for a very large velocity capture range by maintaining the same cooling rate allowed by the single mode lasers. A large fraction of the circulating ions are expected to be cooled both in coasting and bunched beams. The device, which does not use an active medium, can easily operate at any frequency from UV to IR spectral region. This revised version was published online in August 2006 with corrections to the Cover Date.     

Gas diffusion induced by resonance light field

The physical interpretation of a light-induced gas diffusion phenomenon is given and the experimental observation of this phenomenon in Na vapors is reported. It is established that Na vapors resonantly interacting with radiation can move along or against the direction of light propagation due to collisions with a buffer gas.