[en] One hundred fifty-six ¹²CH₃F overtone absorption lines, comprised between 11 545 and 11 836 cm⁻¹, have been observed by using a tunable diode laser (TDL) spectrometer. Their intensities range around 10⁻²⁶ cm/molecule and have been measured by utilizing commercial AlGaAs/GaAs laser diodes through the wavelength modulation (WM) and the 2nd harmonic (2f) detection techniques. Self-broadening coefficients and line strengths have been measured at room temperature for seven of the strongest transitions, while air-broadening coefficients have been obtained for two lines. In addition, self- and air-collisional shifts have been measured for the 11 564.25 cm⁻¹ transition. -- Highlights: • Many methyl fluoride absorption lines have been observed at 845–865 nm. • Laser diodes sources and the frequency modulation technique permit fine spectroscopy. • Absorption cross sections as low as 1×10⁻²⁶ cm²/molecule have been detected. • Pressure broadening and shift coefficients have collected for the more intense lines

[en] A theoretical model is proposed to explain the plasma production occurring in alkali vapours irradiated by c.w. dye-lasers tuned to the resonance transition. The nX levels, with energy nearly twice that of the excitation, are populated by the energy pooling collision between two laser-excited atoms and hence are ionized by the process of photoionization and collision with a third excited atom. The electron density is further enhanced by electronic-impact ionization from the nX levels until the stationary state of the plasmas is achieved. The theoretical fluorescence behaviour of some test levels as a function of the characteristic parameters (laser power, temperature) is compared with the experimental results obtained in potassium vapours. (author)

[en] Collisional broadening and shift coefficients have been obtained by analyzing the line shapes of oxygen absorptions in the 760 nm electronic band. By using a diode laser spectrometer with commercially available etherostructure Al_xGa_1-xAs diode lasers operating in 'free-running mode', line shape parameters have been collected at room temperature by varying the gas pressure. A systematic study has been carried on seven absorption lines by scanning the diode laser emission wavelength around the gas resonances. The weak absorption lines have been detected by using the wavelength modulation (WM) spectroscopy technique with second-harmonic detection

[en] We report an investigation of collisional processes in Ca vapour in the presence of noble gases under ¹S_o→¹P₁ laser excitation. We observe the process of energy transfer to the triplet ³P_J (J=1, 3) states and the process of energy pooling to many higher energy states. The combination of these processes makes it possible, by changing pressure and kind of noble gas, to 'drive' the population distribution of the upper states. (Author)

[en] Cosmic ray interactions can be investigated indirectly in γ ray astronomy, with the observation of spectral and morphological features of certain classes of sources. MAGIC is a stereoscopic system of two γ ray telescopes, located at La Palma (Canaries), with access to the energy window between 50 GeV and 30 TeV. Sources of high relevance for the study of very high energy hadronic interactions are active galactic nuclei, as blazars and radio galaxies. MAGIC has detected about fifty such extragalactic objects; we will present some where the emission is explained with accelerated hadrons in interaction with ambient photons. We will also mention cosmic ray acceleration in galaxy clusters. Other than that, hadron-hadron interactions are supposed to take place in some supernova remnants in interaction with surrounding molecular clouds; we will show some results, in connection with cosmic rays of galactic origin. Finally, about other possible components, we will mention the measurement of the diffuse electron and positron spectrum. Trustingly, the close connection between particle physics and astrophysics will contribute in future years to many new interesting observations. (authors)

[en] Two blue lines (406.7 nm and 413.1 nm) of a Kr⁺ laser have been used to excite the potassium dimer K₂. It has been analysed the spectral region between 400 nm and 800 nm where a rich fluorescence spectrum has been observed as the result of different decay processes. Some of these features have not been reported previously; in particular it is interpreted the blue fluorescence( ∼ (400-470)nm) as due to the C → X and D →X bands, as indicated also by the absorption spectra recorder in this region for different temperatures

[en] Energy pooling in alkali vapour mixtures has been previously investigated by us in an amalgam of sodium and potassium. In this paper the peculiar features appearing when some buffer gas is introduced in the cell are described. It is demonstrated that the buffer gas enhances the energy transfer between Na(3P) and K(4S), which is detected through the effects induced on the highly excited states populated by the Na(3P)/Na(3P) and K(4P)/K(4P) collisions

[en] We show two color spectroscopic measurements that we have done on cold rubidium atoms confined in a magneto-optic trap. The measurements have been done on both Rb isotopes by exciting the 8s_1/2, 5d_3/2, and 5d_5/2 states from the trapping 5p_3/2 level. The obtained lineshapes show the presence of the Autler-Townes splitting induced by the strong trapping laser. The hyperfine constants of the 5d levels have been derived

[en] The results of an experiment on the associative ionization collision between sodium and cesium excited atoms are reported. The atoms are excited by two resonant cw lasers to the 3P_3/2 and 6P_3/2 levels, respectively, and the formation of the NaCs⁺ molecular ion is observed. The rate constant of such process has been measured relative to the known rate constant of sodium associative ionization and its value resulted in K=(5.4±3.2)x10^-11 cm³ s^-1

[en] The rate constants of the energy-pooling collisions in the Na-Rb and K-Rb vapor mixtures, resonantly excited by two cw dye lasers, have been measured relative to a known energy-pooling rate constant of a homonuclear reaction. To isolate the heteronuclear contribution in the fluorescence spectrum, a double-modulation technique has been adopted. The effective lifetimes of the excited levels that explicitly appear in the solution equation have been directly measured by using pulsed lasers. A discussion about the collision cross-section dependence on the energy defect involved in the energy-pooling collisions is reported