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Microwave Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Alfons Dehé, K. Beilenhoff, K. Fricke, H. Klingbeil, V. Krozer, H.L. Hartnagel
Cavities are used in a variety of applications. For example, they can be used to construct filters, and they serve as those elements in microwave generators (e.g., klystrons) that determine the operating frequency. Cavities can also be applied in order to measure the frequency or the wavelength of microwaves (wavemeter). The most important parameters of a cavity are its resonant frequency and its Q-factor. The latter determines the sharpness of the resonance or, in case of filters, the bandwidth of the passband.
High-resolution spectroscopy of the ν3 antisymmetric C–H stretch of C2H2 + using leak-out action spectroscopy
Published in Molecular Physics, 2023
Stephan Schlemmer, Eline Plaar, Divita Gupta, Weslley G. D. P. Silva, Thomas Salomon, Oskar Asvany
In both action spectroscopy campaigns, we used continuous-wave (cw) high-resolution optical parametric oscillators (OPOs), operating in the spectral region, as IR light sources. For the LOS campaign, we used a commercial Aculight Argos Model 2400 C. The IR beam entered the vacuum environment via a 0.6 mm thick diamond window (Diamond Materials GmbH), traversed the 22-pole trap, and exited the vacuum system via a CaF window after which it was absorbed by a power meter. This power was on the order of 200 mW. The irradiation time was controlled by a laser shutter (Thorlabs model SH05). The frequency of the IR radiation has been measured by a wavemeter (Bristol model 621A) with an accuracy of (in case it is well adjusted). We did additional calibration measurements with neutral contained in an absorption cell, whose exact frequencies are given in the HITRAN database [19]. After the calibration, we shifted our data up by . With this procedure, the accuracy of the data is expected to be on the order of .
Precision measurement of quasi-bound resonances in H2 and the H + H scattering length
Published in Molecular Physics, 2022
K.-F. Lai, E. J. Salumbides, M. Beyer, W. Ubachs
The frequency calibration of the spectroscopy laser, probing the excitation of quasi-bound resonances to the F0-outer well state, is crucial because it determines the accuracy at which the energy of those resonances are determined. This laser is a travelling-wave Pulsed-Dye-Amplifier (PDA) amplifying the output of a continuous-wave (CW) ring-dye-laser, upon-frequency doubling delivering a pulsed output with a frequency bandwidth of MHz [55]. The absolute frequency calibration relies on saturated absorption spectroscopy of hyperfine-resolved using the CW-output of the ring laser as well as a wavemeter (Toptica High-Finesse WSU-30) [56]. Effects of frequency chirp in the pulsed output of the PDA is analysed and corrected for, following established methods [55]. Excitation of the two-photon transitions is established in a Doppler-free geometry with counter-propagating beams aligned in a Sagnac interferometric scheme [57].
The electronic system
Published in Molecular Physics, 2022
Julia Gerschmann, Erik Schwanke, Silke Ospelkaus, Eberhard Tiemann
10 g of Ca are placed in the hottest section (approx. 950) of the heat pipe. The section with 9 g of Li is kept at 620 – 660. The other side with Ca, facing the spectrometer, is held at 780 – 790. The thermal emission is recorded with a Fourier transform spectrometer (IFS 120 HR, Bruker) set at a resolution of 0.02 cm. The spectrum is provided in ASCII format as supplementary material [15]. Fluorescence is generated with a single mode diode laser stabilised to a wavemeter, and the LIF spectra are recorded with a resolution of 0.05 cm by the FT spectrometer simply to save time.