Methyl alcohol is the most important lasing molecule in the Far-Infrared (FIR) spectral region, and the most widely used for investigation and for applications. Since the last critical review of 1984, over seventy papers have been published dealing with the FIR laser lines and the infrared spectroscopy of CH3OH. In 1984 we could list about 330 FIR laser lines, 98 of which were measured in frequency and 105 assigned. Since then more than 70 papers were published increasing the number of the known laser lines to 575 (103 measured in frequency). Also the FIR and IR spectroscopy was largely improved thanks to the analysis of high resolution FT spectra, and the number of the correctly assigned laser lines has been increased to 224. The wavenumbers of the assigned lines can now be predicted with an accuracy of about 0.001 cm−1 or better, thus approaching the accuracy of the experimental frequency measurements.

We have used our new pulsed CO2 laser, operating both on regular and hot bands, to excite the (CD3OH)-C-13 methanol isotopomer. This has lead to the observation of 13 new high-threshold far-infrared laser emissions (also identified as terahertz laser lines), with frequencies in the range between 24.11 and 102.56 cm(-1) (0.72-3.07 THz). The absorption transitions leading to these new FIR laser emissions have been located by observing the optoacoustic absorption spectra around the CO2 emissions. Here, we present these new far-infrared laser lines, characterized in wavelength, polarization, offset relative to the center of the pumping CO2 laser transition, relative intensity, and optimum operation pressure.

Although conservation and biogeography of insular populations have been widely addressed, it is often difficult to obtain complete floral and faunistic catalogues. However, comparisons of standardised sample collections may represent a valuable short-cut in investigating insular biogeography. For Lepidoptera, several methods have been proposed to obtain them, but they generally require the presence of the researchers in situ and usually collect one diurnal or nocturnal species only. Butterflies and moths collected by Malaise traps in two years of research in the Tuscan Archipelago were analysed: it was found that Lepidoptera biodiversity in these islands is mainly determined by present day island isolation, as recently shown for the Aegean Archipelago. Moreover, the pattern of similarity among the Lepidoptera collected in the six islands by Malaise traps reflects the general Tuscan Archipelago biogeographic paradigm. In conclusion, this could represent a simple and cheap method to obtain valuable data for conservation and biogoegraphic analyses, mainly when the areas under study are difficult to reach.

The aim of this paper is to examine whether current and/or Pleistocene geography affects the pattern of species richness and composition in two families of flying Hymenoptera in the Tuscan Archipelago (Italy). Faunistic data were obtained from the literature and from our own surveys. We used the Spearman rank correlation test to assess the influence on the richness of present-day and Pleistocene island area and isolation. Moreover, we searched for patterns of similarity among the six examined islands of Tuscan Archipelago, with the adjacent Tuscan mainland and Sardinia and Corsica islands by cluster analysis (UPGMA) and by parsimony analysis of endemicity (PAE). Moreover, we verified whether the percentage of typical species of Tuscany and Sardo-Corsican area is related to the recent and/or palaeogeographical distances of the islands from the two main fauna source pools. Isolation is the best predictor for species richness while Pleistocene area and Pleistocene isolation do not show any significant correlation. Cluster analysis and PAE show a biogeographic pattern where generally Capraia and Montecristo group together with Corsica, while Elba, Giglio, and Pianosa group with Tuscan mainland. Recent geography seems to also affect fauna compositions. Indeed the incidence of Tuscan and Sardo-Corsican species is related to the present-day island distance to Tuscany and Corsica. In conclusion, we strongly suggest that colonization of these islands acted by dispersal from Tuscany and Corsica, using Elba island as a stepping stone.

We have investigated a high-resolution Fourier transform (FT) absorption spectrum of the 13CH3OH isotopomer of methanol from 400 to 950cm−1 with the “Ritz” program. We present the assignments of 7160 transitions, 3021 of which belong to A-symmetry, and 4139 to E-symmetry. These transitions occur between states labeled by K quantum numbers up to 14, and by torsional quantum numbers n up to 4. The “Ritz” program evaluated the energies of the 4684 involved levels with an accuracy of the order of 10−4cm−1. All of the assigned lines correspond to transitions involving torsionally excited levels within the ground small-amplitude vibrational state.

Using a novel CO2 pulsed laser that presents high peak power (several hundreds of watts) together with high spectral purity, we have reinvestigated the CH3OD isotopomer of methanol as a source of far infrared laser emissions pumped by the 10P and 10HP CO2 laser lines. Thirty-five new lines have been observed and characterized for wavelength, offset, relative polarization, optimum operation pressure and relative intensity.

A novel pulsed power supply for gas lasers is presented. The device uses only solid state components and is based on a capacitor bank discharge. Fast switching of the discharge is triggered by an insulated gate bipolar transistor. The terminal section of the power supply is a transformer designed to match the reactive capacitance of a gas discharge. Strokes up to 30 kV and 30 mA are achieved across the secondary windings of this transformer. The power supply delivers high voltage pulses with a duration between 0.5 and 50 μs and a repetition rate up to some kHz. The power supply has been tested on a longitudinal discharge quasi-cw regime CO2 laser. Laser pulses were generated with a duration down to the microseconds region, a peak power exceeding some kilowatts, and a repetition rate ranging from 200 Hz to a few kHz.

Our new waveguide pulsed CO2 laser, with peak powers above 1 kW, has allowed us to observe 24 new far-infrared laser lines emitted by hydrazine. Each of them is characterized in wavelength, relative polarization, intensity, optimum operating pressure and pump offset from the center of the exciting CO2 line. These new laser emissions either form pairs sharing the same pump line, or complete such pairs with lines known from the literature. In the latter case, we have measured the relative polarization and offset of the partner lines whenever they were not reported in the literature. The availability of laser systems with two emission lines orthogonally polarized and sharing the same upper level is expected to facilitate the assignment work. We present complete assignments for four FIR laser emissions, and we propose J and K values for 12 further laser systems.

We present a technique for generating short far-infrared (FIR) laser pulses, with a linewidth close to the Fourier transform limit, changing the reflectivity of an InSb crystal by the photoelectric effect. The crystal is irradiated with an optically pumped CW FIR laser and its reflectivity at an FIR frequency is changed by the ionizing radiation of a pulsed Nd-YAG laser. A reflectivity change, from 18 to 90%, has been obtained. Shorter FIR pulses can be obtained using shorter ionizing laser pulses. Finally, double pulses separated by an arbitrary time interval and of chosen amplitude are obtained.

Using for the first time a waveguide CO2 laser with a tunability of 300 MHz, in order to pump large offset infrared absorptions, we obtained 34 new far-infrared laser lines from the hydrazine molecule; their wavelengths range from 155.2 to 669.3 mu m. All of the new lines and some other already known laser emissions are characterized in the wavelength, the polarization relative to that of the pumping CO2 laser, the optimum pressure of operation, relative intensity, and the offset relative to the CO2 center frequency.

We present preliminary data on the performance of a new fast photodetector based on a W–InSb metal-insulator-semiconductor point contact diode operating at room temperature and with no bias voltage. The device can work either as a video detector or as harmonic mixer for radiation from far–infrared (FIR) to visible. In the FIR region, for wavelengths from 200 to 400 μm, the W–InSb point contact diode showed a sensitivity comparable to that of Golay cells. In the visible region the device showed a video and heterodyne detection responsivity much higher with respect to standard M.I.M. point contact diodes. Owing to its ruggedness, low cost and wide band of operation, the W–InSb point contact diode may be very attractive as a general purpose optical sensor.

We used for the first time a waveguide CO2 laser of large tunability to pump H13COOH; we report 16 new far infrared laser lines, whose wavelengths range from 185.3 to 1219.9 μm. All the new lines are characterized in wavelength, polarization relative to that of the CO2 laser, optimum pressure of operation and offset relative to the center frequency of the pumping laser; we report also new measurements of offset and polarization for some known FIR lines. Moreover, we present tentative assignments for seven of the new FIR laser transitions in the υ6 band.

The "Ritz" computer program, developed for facilitating the assignment of molecular Fourier transform absorption spectra and described in a previous work, determines the energy level values involved in the assigned transitions by the Rydberg-Ritz combination principle. Combining the data obtained from the analyses of high-resolution infrared (IR) and far-infrared (FIR) spectra, it is possible to predict possible FIR laser emissions of molecules. In the present work we have applied this method to the common isotopomer methanol, 12CH3 16OH, and obtained 14 proposed assignments for previously unassigned FIR laser lines. We also predict 15 possible new FIR laser emissions. For the first time, an assignment involving a four-level laser system with collisional population transfer to a slightly higher energy level is reported. Copyright 1998 Academic Press.

We present here a project for the industrial development of a new magnetometer that is intended to achieve the highest performance in measuring geomagnetic field. The instrument is based on the well-known technology of optically pumped alkali vapour magnetometers. Unlike current commercial models, a diode laser replaces the traditional radio-frequency lamp as pumping source and our magnetometer uses potassium as reference atom, contrary to the more traditional cesium or rubidium. The advantages of this choice are discussed. Preliminary experimental results on a prototype show an expected accuracy better than 1 pT/Hz-1/2.

We measured the dependence of the reflectivity of InSb crystals upon temperature in the submillimeter region using monochromatic radiation from an optically pumped far infrared (FIR) laser. The measures allowed us to determine the value of the electron effective mass at low temperatures with radiations of different frequencies. Our measurements extend the results obtained recently on pure crystals with magneto-optical methods to the low temperatures region where only old measures were available.

We present ten new far-infrared (FIR) laser lines obtained by optically pumping ethyl chloride by means of a CW waveguide CO/sub 2/ laser with a tunability range of 300 MHz. By means of a heterodyne technique and using, as mixing element, a metal-insulator-metal (MIM) point contact diode or a new home built metal-semiconductor diode, we measured the frequency of all these new lines, as well as tha...

We report the observations of the decays B+ → ψ(2S)K+ and B0 → ψ(2S)K∗(892)0 in pp̄ collisions at a center-of-mass energy of 1.8 TeV using a 110 pb−1 data sample recorded by the Collider Detector at Fermilab. We also reconstruct the decays B+ → J/ψK+ and B0 → J/ψK∗(892)0 and measure the six ratios of branching fractions of these four decays. The relative branching-fraction results are shown to be consistent with phenomenological factorization calculations of hadronic B-meson decays. We use the world-average branching fraction B(B+ → J/ψK+) to derive B(B+ → ψ(2S)K+) = (0.56±0.08±0.10)×10−3 , B(B0 → ψ(2S)K∗(892)0) = (0.92± 0.20±0.16)×10−3, and B(B0 → J/ψK∗(892)0) = (1.78±0.14±0.29)×10−3 , where the first and second uncertainties are statistical and systematic, respec-

Ten new FIR laser lines have been recently observed in C2H5Cl. We assign them to absorptions in the A-type ν9 band of C2H5 35Cl. From their assignment we could identify some more absorption lines in the high resolution optoacoustic spectrum of this molecule, obtained using CO2 lasers with a tunability of 1 GHz around each line. The theoretical analysis of the spectrum has been extended from Jmax=23 to Jmax=64. Further improvements need a better knowledge of the centrifugal coefficients in the fundamental vibrational level. We also give new values of the molecular constants of C2H5 35Cl in the excited vibrational level.

The frequencies of the different Zeeman components of the neutral calcium metastable (4s, 4p) P-3(1) and P-3(2) levels were measured in a highly homogeneous magnetic field of the order of 0.4 T by a double-resonance technique in an atomic metastable beam. The Lande factor of the two levels was determined as g(J)(3P1) = 1.5010829(28) and g(J)(P-3(2)) = 1.5011308(75). (C) 1998 Optical Society of America [S0740-3224(98)00208-2] OCIS codes: 020.0020, 020.7490, 300.6320.

The measurement of the optical transmission through the plasma of a laser beam, swept in frequency around the resonance absorption lines of atomic or ionic species, allows the direct acquisition of new information on the kinetics of both neutral and ionic species, separating the contributions of the different components of the plasma. The high intensity of the laser allows one to obtain a good signal-to-noise ratio in absorption spectroscopy, even in the presence of the high luminous background of the plasma. This technique has been applied to several experimental condition. We have studied the plasma parameters of an Ar laser tube discharge in a current densities range between 400 and 1200 A/cm(2). Both transitions leaving from the neutral 1s(5)(P-3(2)) metastable level (in the near IR) and from the metastable or long-lived 3p(4)(P-3)3d(4)F ionic levels were observed (in the red). Information was obtained about the temperatures, the population densities in the metastable states, and the cataphoretic speed in the discharge both for neutral and for single-ionized species. Particular care was devoted to investigate the properties of the discharge in a transverse magnetic field, which is able to enhance the laser emission power.