- 标题
- 摘要
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- 实验方案
- 产品
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Handbook of Exoplanets || Spectroscopic Direct Detection of Exoplanets
摘要： The spectrum of an exoplanet reveals the physical, chemical, and biological processes that have shaped its history and govern its future. However, observations of exoplanet spectra are complicated by the overwhelming glare of their host stars. This chapter focuses on high-resolution spectroscopy (HRS) (R D 25;000–100;000), which helps to disentangle and isolate the exoplanet’s spectrum. At high spectral resolution, molecular features are resolved into a dense forest of individual lines in a pattern that is unique for a given molecule. For close-in planets, the spectral lines undergo large Doppler shifts during the planet’s orbit, while the host star and Earth’s spectral features remain essentially stationary, enabling a velocity separation of the planet. For slower-moving, wide-orbit planets, HRS, aided by high contrast imaging, instead isolates their spectra using their spatial separation. The lines in the exoplanet spectrum are detected by comparing them with high resolution spectra from atmospheric modelling codes; essentially a form of ?ngerprinting for exoplanet atmospheres. This measures the planet’s orbital velocity and helps de?ne its true mass and orbital inclination. Consequently, HRS can detect both transiting and non-transiting planets. It also simultaneously characterizes the planet’s atmosphere, due to its sensitivity to the depth, shape, and position of the planet’s spectral lines. These are altered by the planet’s atmospheric composition, structure, clouds, and dynamics, including day-to-night winds and its rotation period. This chapter describes the HRS technique in detail, highlighting its successes in exoplanet detection and characterization, and concludes with the future prospects of using HRS to identify biomarkers on nearby rocky worlds and map features in the atmospheres of giant exoplanets.
关键词： atmospheric characterization,molecular features,exoplanets,Doppler shifts,high-resolution spectroscopy
更新于2025-09-23 15:21:01
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The upGREAT dual frequency heterodyne arrays for SOFIA
摘要： We present the performance of the upGREAT heterodyne array receivers on the SOFIA telescope after several years of operations. This instrument is a multi-pixel high resolution (R&107) spectrometer for the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA). The receivers use 7-pixel subarrays configured in a hexagonal layout around a central pixel. The low frequency array receiver (LFA) has 2x7 pixels (dual polarization), and presently covers the 1.83-2.06 THz frequency range, which allows to observe the [CII] and [OI] lines at 158μm and 145μm wavelengths. The high frequency array (HFA) covers the [OI] line at 63μm and is equipped with one polarization at the moment (7 pixels, which can be upgraded in the near future with a second polarization array). The 4.7 THz array has successfully flown using two separate quantum-cascade laser local oscillators from two different groups. NASA completed the development, integration and testing of a dual-channel closed-cycle cryocooler system, with two independently operable He compressors, aboard SOFIA in early 2017 and since then, both arrays can be operated in parallel using a frequency separating dichroic mirror. This configuration is now the prime GREAT configuration and has been added to SOFIA’s instrument suite since observing cycle 6.
关键词： SOFIA (GREAT),high resolution spectroscopy,THz astronomy,airborne
更新于2025-09-23 15:21:01
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - N ovoFEL as Source of Powerful Ultramonochromatic Tunable Terahertz Radiation
摘要： Laser nature of a continuous pulse-periodical radiation of the Novosibirsk free-electron laser (NovoFEL) appears in a good coherency of its pulses and very narrow synchronized longitudinal modes. Filtration of one of the modes by a system of three resonance Fabry-Perot interferometers allows to create laser source with monochromaticity which is sufficient for typical high-resolution THz spectroscopy (δf/f ≤ 5·10-8, δf ≤ 0.1 MHz). Features of the source compared to other alternative devices are a wide tuning range (1.5-3 THz) and much more high output power (up to 50-100 mW).
关键词： high-resolution spectroscopy,Fabry-Perot interferometers,monochromaticity,NovoFEL,terahertz radiation
更新于2025-09-23 15:21:01
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Numerical study of comb-based high-accuracy distance measurement utilizing VIPA interferometry
摘要： The ultrahigh-precision distance measurement based on a single laser frequency comb as the multi-wavelength source together with an ultra-high-resolution dispersive spectrometer utilizing a virtually imaged phase array (VIPA) was studied numerically. The simulations provide the component parameter optimization and the comb spectral images on a CCD camera. An ameliorated scheme was proposed through achieving real-time comparisons between the reference and interference signals captured on a camera simultaneously to improve both the measurement accuracy and the precision signi?cantly. With the optimized data processing, the proposed approach is especially suitable for serving as a ultra-high precision relative distance measurement, and the measurement resolution can reach picometer scale in the optimal cases.
关键词： Ultra-high precision distance measurement,Ultra-high resolution spectroscopy,Laser frequency comb,Virtually imaged phase array interferometry
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Frequency Comb Photoacoustic Spectroscopy
摘要： Photoacoustic spectroscopy (PAS) based on continuous wave (cw) lasers provides high absorption sensitivity in small sample volume [1, 2] but it is usually restricted to single species detection because of the limited tunability of cw lasers. Broadband PAS has been demonstrated using cantilever-enhanced detectors in combination with incoherent [3] or supercontinuum [4] light sources modulated by conventional Fourier transform spectrometers (FTS), however, the spectral resolution was limited to a few cm-1. Here we report the first demonstration of optical frequency comb photoacoustic spectroscopy (OFC-PAS), which combines the wide spectral coverage and high resolution of frequency combs with the small sample volume of photoacoustic detection [5]. The OFC-PAS setup is based on a doubly-resonant optical parametric oscillator pumped by a femtosecond Tm:fiber laser with a repetition rate of 125 MHz. The intensity of the signal output centered at 3.3 μm is modulated at ~500 Hz using an FTS. One output of the FTS (4.8 mW of signal power) is directed to a 10-cm-long cantilever-enhanced photoacoustic cell with 8 mL volume (Gasera, PA201), while the other is measured with a photodetector and used for normalization of the PA spectrum. Figure 1(a) shows in red the room temperature OFC-PAS spectrum of the C-H stretch band of 100 ppm of CH4 in N2 at 1000 mbar and 1 GHz resolution (left axis) recorded in 200 s (no averaging). The blue curve shows the simulated absorption coefficient, (cid:68), based on the parameters from the HITRAN database (right axis). A zoom-in around the Q-branch region at 1000 mbar and 400 mbar is shown in Figs 1(b) and 1(c), demonstrating the high spectral resolution, no instrumental lineshape distortion, and good agreement with the simulation. The limit of detection (LOD), evaluated from the signal to noise ratio of the methane line at 3058 cm-1 at 1000 mbar, is 0.8 ppm in 200 s for power spectral density of 42 μW/cm-1. While this LOD is comparable to those obtained with other broadband PAS methods [3, 4], the resolution of OFC-PAS is more than two orders of magnitude better. The normalized noise equivalent absorption at 1000 mbar is 8 × 10-10 W cm-1 Hz -1/2, comparable to values reported with PAS based on cw lasers [2]. OFC-PAS thus extends the capability of optical sensors for high-resolution multicomponent trace gas analysis in small sample volumes.
关键词： high-resolution spectroscopy,optical frequency comb,trace gas analysis,Photoacoustic spectroscopy
更新于2025-09-12 10:27:22
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Fine structure in high resolution 4f7?4f65d excitation and emission spectra of X-ray induced Eu2+ centers in LuPO4:Eu sintered ceramics
摘要： X-ray induced effects in LuPO4:Eu3+ sintered thermoluminescent material were investigated by absorption and photoluminescence measurements between 20-300 K. Evidence for Eu3+→Eu2+ conversion upon exposure to X-rays was obtained as narrow band blue Eu2+ photoluminescence was observed. The low temperature luminescence of Eu2+ ions in X-rayed LuPO4:Eu ceramics showed a unique fine structure with a sharp zero-phonon line at 425.8 nm and well-resolved vibronic structure. Excitation spectra of the Eu2+ luminescence revealed a rich structure in which individual 4f7→ 4f6(7FJ)5d1 zero-phonon lines accompanied by vibronic transitions were identified. A detailed analysis allowed an accurate calculation of the Eu3+-like 4f6(7FJ) core levels in the 4f65d1 excited configuration. The 4f6 core splitting is different from that of the 7FJ states for Eu3+ in LuPO4, providing evidence for the role of 4f6-5d interaction on the splitting of the 4f6 configuration. The unique luminescence of Eu2+ with a small Stokes shift and well-determined energies of 4f6(7FJ)5d1 excited states make LuPO4:Eu a model system for testing theoretical models which are presently developed to calculate and predict the energy level structure and Stokes shift of 4fn-4fn-15d1 transitions of lanthanides.
关键词： Eu2+ luminescence,LuPO4,zero-phonon line,high resolution spectroscopy,4f65d excited state
更新于2025-09-09 09:28:46