| 1. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Measurement and assignment of double-resonance transitions to the 8900-9100- cm-1 levels of methane
- 2021
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 103:2
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Tidskriftsartikel (refereegranskat)abstract
- Optical-optical double-resonance spectroscopy with a continuous wave pump and frequency comb probe allows measurement of sub-Doppler transitions to highly excited molecular states over a wide spectral range with high frequency accuracy. We report on assessment and characterization of sub-Doppler double-resonance transitions in methane measured using a 3.3-μm continuous wave optical parametric oscillator as a pump and a 1.67-μm frequency comb as a probe. The comb spectra were recorded using a Fourier transform spectrometer with comb-mode-limited resolution. With the pump tuned to nine different transitions in the ν3 fundamental band, we detected 36 ladder-type transitions to the 3ν3 overtone band region, and 18 V-type transitions to the 2ν3 overtone band. We describe in detail the experimental approach and the pump stabilization scheme, which currently limits the frequency accuracy of the measurement. We present the data analysis procedure used to extract the frequencies and intensities of the probe transitions for parallel and perpendicular relative pump-probe polarization. We compare the center frequencies and relative intensities of the ladder-type transitions to theoretical predictions from the TheoReTS and ExoMol line lists, demonstrating good agreement with TheoReTS.
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| 2. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Sub-Doppler Double-Resonance Spectroscopy of Methane Using a Frequency Comb Probe
- 2021
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 126:6
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of sub-Doppler molecular response using a frequency comb by employing the comb as a probe in optical-optical double-resonance spectroscopy. We use a 3.3 μm continuous wave pump and a 1.67 μm comb probe to detect sub-Doppler transitions to the 2ν3 and 3ν3 bands of methane with ∼1.7 MHz center frequency accuracy. These measurements provide the first verification of the accuracy of theoretical predictions from highly vibrationally excited states, needed to model the high-temperature spectra of exoplanets. Transition frequencies to the 3ν3 band show good agreement with the TheoReTS line list.
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| 3. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Double-Resonance Spectroscopy of Methane Using a Comb Probe
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - : IEEE Lasers and Electro-Optics Society. - 9781665418768
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Konferensbidrag (refereegranskat)abstract
- Optical-optical double resonance (OODR) spectroscopy is a powerful tool for the experimental assignment of highly-excited molecular states, which in turn is needed for verification of the accuracy of theoretical predictions of high-temperature spectra observed in exoplanets and in combustion environments. Previous implementations of OODR used either continuous wave (cw) lasers, which limit the number of transitions that can be detected, or pulsed lasers, which limit the spectral resolution. Recently, we demonstrated OODR with a cw pump and a frequency comb probe and applied it to the detection and assignment of methane transitions in the 3ν 3 ← ν 3 range with sub-Doppler resolution over 200 cm -1 of bandwidth [1]. The pump [see Fig. 1(a) ] was a 1 W 3.3m idler of a cw optical parametric oscillator (cw-OPO), stabilized to the Lamb dip in a selected CH 4 transition in the ν 3 band using a signal from a reference cell. The probe was an amplified fully-stabilized Er:fiber comb ( f rep = 250 MHz), whose center wavelength was shifted to 1.67m using a soliton self-frequency shift fiber (SSSF). The sample of pure CH 4 was contained in an 80-cm-long single-pass cell cooled by liquid nitrogen. The probe spectra were detected using a Fourier transform spectrometer (FTS) with comb-mode-limited resolution [2] , and the final interleaved spectra had 2 MHz sampling point spacing. Figure 1(b) shows the 3ν 3 ← ν 3 R(1) transition at 6046.36008(5) cm -1 , detected with the pump on the ν 3 R(0) line. We measured, fit and assigned 36 probe transitions with the pump tuned to 9 different transitions. Figure 1(d) shows a comparison of the probe transition wavenumbers to predictions from the TheoReTS database [3] , demonstrating agreement within 1 cm -1.
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| 4. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Optical-optical double-resonance spectroscopy of methane using a cavity-enhanced comb probe
- 2021
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Ingår i: OSA Technical Digest. - : Optical Society of America. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We implement a cavity to enhance the absorption of a frequency comb probe in a double-resonance measurement of sub-Doppler 3ν3 ← ν3 methane transitions. This yields two orders of magnitude better sensitivity in 15 times shorter acquisition time compared to previous work using a single-pass cell.
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| 5. |
- Silva de Oliveira, Vinicius, et al.
(författare)
-
Sub-doppler optical-optical double-resonance spectroscopy of methane using a frequency comb probe
- 2021
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Ingår i: OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES). - : Optical Society of America. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We use a 3.3 µm high-power continuous wave pump and a 1.67 µm comb probe to detect transitions in the 3ν3 ← ν3 range of methane with sub-Doppler resolution over 6 THz of bandwidth. We achieve high absorption sensitivity for the comb probe using an enhancement cavity and a Fourier transform spectrometer with auto-balanced detection.
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