M. Meucci

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 two-level pattern trigger for the MAGIC telescope

Strong scientific motivation are pushing the second generation of ground base Cherenkov telescopes to lower as much as possible their energy threshold. MAGIC will be the biggest single telescope, in terms of collection area (250 m 2 ), foreseen for the second-half of 2001. The large collection area, the newphotodetector and the electronic design will allow the telescope to lower the energy threshold below 30 GeV. For this telescope a two-level pattern trigger is designed to work in severe high pixel rate. The MAGIC trigger architecture and its implementation is presented. # 2001 Elsevier Science B.V. All rights reserved. PACS: 95.55.Ka

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.

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.

Energy-pooling ionization and electron - ion recombination measurements in indium

The formation of electrons and ions in the collision between two indium atoms excited to the level is reported. The ionization cross sections and the recombination coefficient for the subsequent electron/ion recombination are measured.

Cholinergic and glutaminergic control of hippocampal RSA during behavior in rabbits.

An experimental model, with novel environmental stimuli, has been used in order to study the effects of cholinergic and glutaminergic modulation on hippocampal electrical activity and behavior. The test consisted in the introduction of a rabbit in an experimental cage in the absence of external stimuli (neutral environment) followed by the introduction into the cage of a novel object containing odorous vegetable branches, a stuffed sparrow-hawk and a live cat. The effects of drug treatments on hippocampal rhythmic slow activity (RSA) parameters (total amount, episode durations and frequency) were studied. Physostigmine (0.1 mg/kg) increased RSA amount both during immobility and movements and was effective only on the frequency of the immobility related RSA. Scopolamine (0.4 mg/kg) reduced the percentage of RSA occurring during immobility and movements and the frequency of the movement related RSA. Glutamic acid diethyl ester (GDEE) (400 micrograms), injected into the dorsal hippocampus, had qualitative effects similar to those obtained with scopolamine, but, quantitatively, they were less pronounced. The combination between GDEE and scopolamine potentiated the effects of the two drugs. Results support the assumption that cholinergic septal input is responsible for hippocampal RSA and the glutaminergic entorhinal input to the hippocampus modulates RSA, probably under cholinergic control.

Dorsolateral PAG neurons: Tonic immobility and morphine effect in freely moving rabbits

The activity of 33 neurons of pontomesencephalic dorsolateral periaqueductal gray matter (PAG), not triggered by motor or sensory stimuli, has been recorded during tonic immobility (animal hypnosis) and after morphine injection (5 mg/kg IV). Several parameters of neural activity were chronically studied, including: frequency, variability and pattern of discharge. Tonic immobility affected the frequency and the variability of the firing rate of the majority of neurons. Morphine decreased frequency and increased variability of 73.3% of the neurons. Maximal morphine effect was observed with a wide range of latencies and was independent of frequency and variability. The negative relationship between frequency and variability recorded during the control period, wa abolished by morphine. Changes in the pattern of discharge were also observed after morphine injections. The effect of tonic immobility and morphine are discussed in the light of the relationships existing between PAG neurons and fear motivated behavior.