Akshay Nataraj


Last Name

Nataraj

First Name

Akshay

ORCID

0000-0002-6287-6847

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2019 - 201912020 - 20234
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Publications 1 - 5 of 5
  • High-Resolution and Gapless Dual Comb Spectroscopy with Current-Tuned Quantum Cascade Lasers
    Item type: Conference Paper
    Gianella, Michele; Nataraj, Akshay; Tuzson, Béla; et al. (2020)
    OSA Technical Digest ~ Conference on Lasers and Electro-Optics
    We measured gapless, high-resolution absorption spectra spanning 55 cm−1 by simultaneous current-modulation of two quantum cascade laser frequency combs. Detector noise limited spectra were obtained in as little as 10 ms with a resolution of a few MHz.
  • Quantum cascade laser absorption spectrometer with a low temperature multipass cell for precision clumped CO2 measurement
    Item type: Journal Article
    Nataraj, Akshay; Gianella, Michele; Prokhorov, Ivan; et al. (2022)
    Optics Express
    We present a quantum cascade laser-based absorption spectrometer deploying a compact (145 mL volume) segmented circular multipass cell (SC-MPC) with 6 m optical path length. This SC-MPC is embedded into an effective cooling system to facilitate operation at cryogenic temperatures. For CO₂, the sample is cooled to 153 K, i.e. close to the sublimation point at 10 mbar. This enables efficient suppression of interfering hot-band transitions of the more abundant isotopic species and thereby enhances analytical precision. As a demonstration, the amount fractions of all three CO₂ isotopologues involved in the kinetic isotope exchange reaction of ¹²C¹⁶O₂ + ¹²C¹⁸O₂ ⇌ 2·¹²C¹⁶O¹⁸O are measured. The precision in the ratios [¹²C¹⁸O₂]/[¹²C¹⁶O₂] and [¹²C¹⁶O¹⁸O]/[¹²C¹⁶O₂] is 0.05 ‰ with 25 s integration time. In addition, we determine the variation of the equilibrium constant, K, of the above exchange reaction for carbon-dioxide samples equilibrated at 300 K and 1273 K, respectively.
  • Spectral Interleaving with Quantum Cascade Laser Frequency Combs
    Item type: Conference Paper
    Gianella, Michele; Nataraj, Akshay; Tuzson, Béla; et al. (2019)
    2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)
  • High-resolution and gapless dual comb spectroscopy with current-tuned quantum cascade lasers
    Item type: Journal Article
    Gianella, Michele; Nataraj, Akshay; Tuzson, Béla; et al. (2020)
    Optics Express
  • Position-Specific Isotope Analysis of Propane by Mid-IR Laser Absorption Spectroscopy
    Item type: Journal Article
    Nataraj, Akshay; Tuzson, Béla; Gianella, Michele; et al. (2023)
    Analytical Chemistry
    Intramolecular or position-specific carbon isotope analysis of propane (13CH3–12CH2–12CH3 and 12CH3–13CH2–12CH3) provides unique insights into its formation mechanism and temperature history. The unambiguous detection of such carbon isotopic distributions with currently established methods is challenging due to the complexity of the technique and the tedious sample preparation. We present a direct and nondestructive analytical technique to quantify the two singly substituted, terminal (13Ct) and central (13Cc), propane isotopomers, based on quantum cascade laser absorption spectroscopy. The required spectral information on the propane isotopomers was first obtained using a high-resolution Fourier-transform infrared (FTIR) spectrometer and then used to select suitable mid-infrared regions with minimal spectral interference to obtain the optimum sensitivity and selectivity. We then measured high-resolution spectra around 1384 cm–1 of both singly substituted isotopomers by mid-IR quantum cascade laser absorption spectroscopy using a Stirling-cooled segmented circular multipass cell (SC-MPC). The spectra of the pure propane isotopomers were acquired at both 300 and 155 K and served as spectral templates to quantify samples with different levels of 13C at the central (c) and terminal (t) positions. A prerequisite for the precision using this reference template fitting method is a good match of amount fraction and pressure between the sample and templates. For samples at natural abundance, we achieved a precision of 0.33 ‰ for δ13Ct and 0.73 ‰ for δ13Cc values within 100 s integration time. This is the first demonstration of site-specific high-precision measurements of isotopically substituted non-methane hydrocarbons using laser absorption spectroscopy. The versatility of this analytical approach may open up new opportunities for the study of isotopic distribution of other organic compounds.
Publications 1 - 5 of 5