1,720,988 research outputs found
TWO-PHOTON ABSORPTION SPECTROSCOPY OF A ¹³CO₂ VIBRATIONAL TRANSITION
No full textTwo-photon absorption spectroscopy is an ideal method for precision measurements of molecular energy levels and trace gas concentration. We report a two- photon absorption of the Q(36) rovibrational transition of ¹³CO₂, measured by cavity- enhanced absorption spectroscopy (CEAS) at λ = 2.8 µm. The high signal-to-noise ratio of two-photon absorption spectra was obtained by optical locking of a narrow-linewidth mid-infrared laser to a high finesse cavity. One longitudinal mode of the cavity was shifted to scan the frequency, calibrated by an optical frequency comb. We studied the properties of the two-photon absorption spectrum. It is expected that this method can be applied in the field of molecular frequency reference and high-sensitivity detection
MOLECULAR BEAM DENSITY MEASUREMENT WITH CAVITY-ENHANCED ABSORPTION SPECTROSCOPY
Full text linkMolecular beams have played an important role in chemical physics research, and beam density is crucial in determining beam properties, reaction rate, and differential cross-section in chemical dynamic experiments. However, few results present the absolute molecular beam density at the moment. We set up an experimental setup that combines the supersonic molecule beam and cavity-enhanced method. The absorption spectrum of carbon monoxide in the beam is continuously recorded when the beam is passing the cavity and we have demonstrated that the absolute molecular beam density can be measured. The absorption spectrum of the CO R₃(0) transition in the beam is shown in figure 1, the beam density can be obtained by measuring the absorption spectrum at different pressures and correcting the effective absorption length. It is expected that with the laser-locked cavity-enhanced method beam density of other molecules, such as C₂H₂, H₂O, CH₄, etc., can be measured quantitatively, which is significant in the crossed molecular beam experiments. This also provides a new method for measuring reaction products in chemical dynamic experiments
Precision Spectroscopy Of Hd
Full text linkPrecision spectral measurement of simple molecules such as H and their isotopes is one of the important research fields of spectroscopy. Combined with accurate calculations, allows us to test the fundamental quantum chemistry theory and to determine the fundamental physical constants such as the proton-to-electron mass ratio. Here we present the Doppler-free spectroscopy measurements of first overtone transition of HD at a temperature as low as 10K, measured the saturated absorption spectrum of the first overtone transition of HD and observed the Doppler free spectral of R (2-0) for the first time. The line profile is different from the saturated absorption spectrum. We analyzed the line profile and it is expected to determine the transition frequency with 11 digits
Narrow linewidth opo light source for precision spectroscopy
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Previous issue date: 23Precision spectroscopy of fundamental bands of molecules in the mid-infrared (MIR) region is of great interest in applications of trace detection and testing fundamental physics, where high-power and narrow-linewidth MIR lasers are needed. By controlling the phase noise of the signal and pump light of a continuous wave optical parametric oscillator (OPO), we established a broadly tunable MIR light source which has an output power of several hundred milliwatts and a linewidth of a few tens kilohertz. The long term frequency drift of the MIR laser was reduced and calibrated utilizing an optical frequency comb. The performance of the light source was investigated and tested by measuring the saturated absorption spectroscopy of a few molecular transitions at 3.3 m
High precision spectrum of the second overtone of 12C16O
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Previous issue date: 6CO is the second most abundant molecule in the universe. Precise spectrum of the carbon monoxide molecule is great importance in astrophysical observation and in the test of the quantum chemistry model. Thirty-nine ro-vibrational transitions of 12C 16O in the second overtone band were measured by a comb-locked cavity ring-down spectrometer. The line positions were determined with kHz accuracy, or relatively 10−12 level, which is over two orders of magnitude more accurate than previous Doppler-limited studies. Comparisons of the line positions determined in this work with literature experimental values and the calculations by the Dunham-Watson model are given. The bond length in the second overtone vibrational state was determined for carbon monoixde. The calculated pure rotational line positions agree with the experimental values recorded by lamb-dip spectrometer within the experimental uncertainties
Narrow Linewidth Opo Light Source For Precision Spectroscopy
Full text linkPrecision spectroscopy of fundamental bands of molecules in the mid-infrared (MIR) region is of great interest in applications of trace detection and testing fundamental physics, where high-power and narrow-linewidth MIR lasers are needed. By controlling the phase noise of the signal and pump light of a continuous wave optical parametric oscillator (OPO), we established a broadly tunable MIR light source which has an output power of several hundred milliwatts and a linewidth of a few tens kilohertz. The long term frequency drift of the MIR laser was reduced and calibrated utilizing a near-infrared optical frequency comb. The performance of the light source was investigated and the laser system will be used for precision measurement of fundamental vibration of HD.Made available in DSpace on 2021-09-24T21:08:44Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
HIGH PRECISION SPECTRUM OF THE SECOND OVERTONE OF 12C16O
No full textCO is the second most abundant molecule in the universe. Precise spectrum of the carbon monoxide molecule is great importance in astrophysical observation and in the test of the quantum chemistry model. Thirty-nine ro-vibrational transitions of CO in the second overtone band were measured by a comb-locked cavity ring-down spectrometer. The line positions were determined with kHz accuracy, or relatively 10 level, which is over two orders of magnitude more accurate than previous Doppler-limited studies. Comparisons of the line positions determined in this work with literature experimental values and the calculations by the Dunham-Watson model are given. The bond length in the second overtone vibrational state was determined for carbon monoixde. The calculated pure rotational line positions agree with the experimental values recorded by lamb-dip spectrometer within the experimental uncertainties
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