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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 161 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a list of more than 800 far-infrared laser lines emitted by optically pumped molecular lasers whose frequencies have been measured. For each line, frequency, wavelength, wave number, lasing molecule, CO2 pump line, and, if available, the assignment of the lasing transition, are given. The list is accompanied by a survey of the techniques of frequency measurement in the far infrared. Accuracies and limitations of the various techniques are also discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 956-960 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dramatic improvements in the stability of the metal-insulator-metal point contact diode has been achieved by the use of blunter whisker tips. The optimum values for tip radius and diode resistance were experimentally determined. Both sensitivity and high-speed response of W-NiO-Ni point contact diodes were investigated at different laser frequencies and mixing orders as a function of tip radius, resistance, and coupling. The tip radii were changed by more than an order of magnitude, and surprisingly, the sensitivity and the harmonic generation up to 88 THz were not significantly affected. A conical antenna was found to be superior to the conventional long-wire antenna at wavelengths shorter than 10 μm. Responsivity measurements as a function of the diode resistance showed evidence for two different physical mechanisms responsible for the operation of the diode.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 10 (1988), S. 941-957 
    ISSN: 0392-6737
    Keywords: Intensities and shapes of atomic spectral lines ; Other topics in atomic spectra and interactions of atoms with photons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono state investigate le forme di riga di transizioni del neon mediante la spettroscopia optogalvanica in intermodulazione. Il segnale intermodulato, privo di allargamento Doppler, è dat da una Lorenziana, corrispondente all'allargamento omogeneo della transizione, sovrapposta ad un fondo Gaussiano dovuto alle collisioni che producono un cambiamento della velocità degli atomi lungo la direzione dei due fasci laser contropropaganti. È stato compiuto uno studio sistematico del contrasto tra il fondo Doppler e l'ampiezza omogenea della riga al variare della pressione del gas e della corrente di scarica. Inoltre, rivelando il neon come traccia in altri gas nobili (argon, elio), si è investigato l'effetto della massa dell'atomo perturbatore nei processi collisionali. I dati sperimentali sono stati confrontati con i modelli teorici esistenti deducendone stime dei parametri collisionali.
    Abstract: Резюме Мы исследуем суб-доплеровские формы линий для переходов неона. Вэаимно модулнрованный сигнал, как обычно, накладывается на шнрокнй гауссов фон, обысловленный соударениями с изменением скоростей Систематически исследуется зависимостй отношения между столкновителйным и однородным сигналами от давленя газа и тока разряда. С целйю детектирования неона, как следа в другнш вуферныш газаш, мы также нзучаем зависимость форм линий от массы других инертиых газов (гелий и аргон). Сравнение теоретических предсказаний и эксперименталйных данных позволяет получнтй количественныэ оценкн параметров соударений.
    Notes: Summary We have investigated sub-Doppler lineshapes of neon transitions by means of intermodulated optogalvanic technique in a direct current hollow cathode and a radio frequency glow discharge. The intermodulated Doppler-free signal, as usual, is superimposed on a broad Gaussian background due to velocity-changing collisions. The ratio between the collisional and the homogeneous signal has been systematically investigated as a function of gas pressure and discharge current. By detecting neon as a trace in other buffer gases, the lineshapes have been also carefully investigated as a function of the mass of the perturbers (helium and argon). Comparison between theoretical predictions and experimental data leads to quantitative evaluations of collisional parameters.
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  • 4
    ISSN: 1432-0630
    Keywords: 42.55H ; 33.60 ; 06.30F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The operation of a cw FIR laser in the presence of a strong electric field is described. A hybrid metal-dielectric waveguide is used and the cavity length is scanned to study how the frequency and power of the laser depend on the field strength. The results have also been checked by heterodyning with a conventional reference laser. We report the results obtained for the 496 μm line of CH3F and the 70.5 μm and 119 μm lines of CH3OH. A large frequency tunability of almost ±40 MHz is obtained in the best case with power levels in the mW range. A very simple theoretical model accounts for the experimental results. We also report the appearance of a new FIR line at about 204 μm when CH3OH is pumped by the 9 μmP(34) of CO2 in the presence of an electric field larger than 1.2 KV/cm.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 38 (1985), S. 255-257 
    ISSN: 1432-0649
    Keywords: 32
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method is proposed, which allows sub-Doppler spectroscopy by means of correlation between photons emitted in atomic cascades. No laser sources are necessary and lineshapes in the absence of strong perturbing electromagnetic fields can be investigated.
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  • 6
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The search for extraterrestrial and, in particular, interstellar molecules has suddenly increased in the last ten years after the discovery of many complex organic molecules by radioastronomy. Since some very interesting lines are not detectable in the radio region, but only in the middle and far infrared, heterodyne techniques seem to be a powerful tool for interstellar line detection in the submillimetric region and the detection of CO at 870 μ in Orion (Philipps and Huggins, 1977) represents an encouraging success for further efforts in this new field of research. In this work the possibility of observing interstellar lines at heterodyne laser wavelengths already available in laboratory has been considered. We also computed relative intensities for some representative rotational lines of interstellar molecules at three typical temperatures (10, 20, 50 K) assuming thermodynamic equilibrium and optically thin regions. The results achieved with heterodyne laser techniques developed in the laboratory are discussed here in order to study the possibility for ground and space astronomical observations.
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  • 7
    ISSN: 1432-0649
    Keywords: 06 ; 35 ; 42.6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Direct frequency measurements of optically pumped far infrared (fir) molecular lasers are reported, also for new lines. This heterodyne technique is versatile and simple. By controlling some parameters of resonator and pump source, possible causes of error are evidenced in the precise frequency determination. The implications for molecular spectroscopy are also discussed.
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  • 8
    ISSN: 1432-0649
    Keywords: PACS: 42.62.Fi; 42.55.Px; 39.30.+w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 , and its sensitivity is 7(2)×10-8 in a 1-Hz bandwidth. The corresponding minimum detectable concentration of CO2 in air has been estimated to be 1 ppm · m. This opens the possibility of a detection at ppb levels at 2 μm, where a two orders of magnitude increase in the CO2 absorption signal is demonstrated.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0649
    Keywords: 32 ; 35 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The optogalvanic technique combined with the excitation by means of a single-frequency dye laser has been used to investigate the nonlinear Hanle effect on a variety of atomic transitions involving various quantum numbers and selection rules. A rate equation model has been successfully applied to provide a quantitative analysis of the observed signals. Saturation and pressure broadening parameters are reported for Ne transitions at 607.4 and 603.0 nm and Ca transitions at 610.2 and 585.7 nm
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  • 10
    ISSN: 1432-0649
    Keywords: PACS: 33.70.Jg; 39.90.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Sensitivity studies are also performed, to evaluate the minimum detectable concentration of HCl in air.
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