Precision Molecular Spectroscopy with Frequency Combs

Gatti, Davide; Sala, Tommaso; Marangoni, Marco; Galzerano, G.; Gianfrani, L.

doi:10.1002/9780470027318.a9249

Cited by 4 publications

(1 citation statement)

References 97 publications

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“…or to a self-referenced optical frequency comb [34]. In both cases the frequency stability can attain the 10 -12 level, corresponding to hundreds of hertz, over times of minutes or even seconds.…”

Section: The Vertical and Horizontal Axesmentioning

confidence: 99%

Laser-Based Primary Thermometry: A Review

Gotti

Lamperti

Gatti

et al. 2021

Journal of Physical and Chemical Reference Data

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Laser-based primary thermometry was initiated almost 15 years ago by the proposal to determine the absolute temperature of a gas at thermodynamic equilibrium through the Doppler width of an associated absorption transition, exploiting the potentially very accurate measurement of an optical frequency to infer the elusive thermal energy of a molecular or atomic absorber. This approach, commonly referred to as Doppler broadening thermometry, has benefited across the years from substantial improvements, of both technical and fundamental nature, eventually reaching an accuracy of about 10 ppm on the temperature determination in the best cases. This is sufficient for Doppler broadening thermometry to play a significant role in the practical realization of the new kelvin, which follows the 2019's redefinition from a fixed value of the Boltzmann constant, and to tackle the challenge, among others, to quantify and possibly fix systematic uncertainties of the international ITS-90 temperature scale. This paper reviews and comparatively analyses methods and results achieved so far in the field of laser-based primary thermometry, also including spectroscopic approaches that leverage the temperature-dependent distribution of line intensities and related absorbances across the ro-vibrational band of a molecular sample. Although at an early stage of development, these approaches show a promising degree of robustness with respect to the choice of the line-shape model adopted for the fitting of the absorption spectra, which is a delicate aspect for all laser-based thermometers. We conclude identifying possible technical and scientific evolution axes of the current scenario.

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Section: The Vertical and Horizontal Axesmentioning

confidence: 99%

Laser-Based Primary Thermometry: A Review

Gotti

Lamperti

Gatti

et al. 2021

Journal of Physical and Chemical Reference Data

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InfraredLIDARApplications in Atmospheric Monitoring

Orr

2017

Encyclopedia of Analytical Chemistry

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The acronym LIDAR stands for LIght Detection And Ranging, an optical analog of RADAR (RAdio Detection And Ranging). The conventional version of LIDAR requires a laser transmitter to launch short pulses of coherent light, which are scattered from atmospheric targets of interest back to an optical receiver, with a time delay that is determined by the range of the target. Optical phenomena in the Earth's atmosphere (e.g. Rayleigh scattering, Raman scattering, Mie scattering, refraction, and resonant absorption) contribute to the amplitude of optical signals returning to the receiver and their characteristic wavelength dependence allows us to measure the concentration and velocity distributions of different atmospheric molecules and aerosol particles. LIDAR backscattering in the infrared (IR) region, on which this article concentrates, is well suited to detecting aerosols (as in clouds or industrial particulate emissions). IR DIAL (DIfferential Absorption Lidar), a variant in which two or more wavelengths are used simultaneously to separate resonant molecular signals from background, enables many molecular species to be monitored by means of their IR absorption spectra. Closely related approaches comprise long‐path IR laser absorption and IPDA (Integrated Path Differential Absorption), with retroreflection from a topographic target (e.g. a strategically located mirror or a hard target, such as the ground in air‐borne applications); these approaches sacrifice optical range information but gain sensitivity because they integrate over all molecules in the optical column between the transmitter/receiver and the reflector or hard target. All of these techniques are vitally dependent on pulsed IR laser technology.

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Isotopologues Detection and Quantitative Analysis by Mid‐Infrared Dual‐Comb Laser Spectroscopy

Vodopyanov

2020

Encyclopedia of Analytical Chemistry

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Isotopologues are molecules that differ from the parent molecule only in their isotopic composition. For example, ordinary light water (H 2 O), semi‐heavy water (HDO), and heavy water (D 2 O) are isotopologues of the same molecule. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent. Isotopologues that differ only by the location of an isotopically modified element are called isotopomers. For example, the 15 N isotope in the N 2 O molecule can be either next to the oxygen atom or second next to it; thus, N 15 NO and 15 NNO are isotopomers of the same molecule. Detecting isotopologues of different molecules is critical in such fields as astrobiology, biogeochemistry, personalized medicine, and forensics, with mass spectrometry being a major technique to distinguish between different isotopologues. In this article, I focus on a new technique for detection of isotopologues based on laser spectroscopy. The backbone of this technology is massively parallel spectroscopic probing in the mid‐infrared spectral region by a frequency comb – a broad spectrum composed of some million phase‐locked equidistant sharp spectral lines – produced by a subharmonic optical parametric oscillator (OPO). Through assessing their unique rotational‐vibrational absorption signatures, we are able to simultaneously detect numerous molecules and their isotopologues in a mixture of gases, in real time and with one part‐per‐billion detection capability.

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Precision Molecular Spectroscopy with Frequency Combs

Cited by 4 publications

References 97 publications

Laser-Based Primary Thermometry: A Review

Laser-Based Primary Thermometry: A Review

InfraredLIDARApplications in Atmospheric Monitoring

Isotopologues Detection and Quantitative Analysis by Mid‐Infrared Dual‐Comb Laser Spectroscopy

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