Nikolai N. Filippov

Determining the vertical structure of CO₂ content is important for studying the exchange of greenhouse gases between the troposphere, where anthropogenic factors determine their growth and content, and the stratosphere. In this work, we analyze the potential information content and vertical resolution of ground-based IR spectroscopy in determining CO₂ profiles from solar radiation measurements with a Bruker 125 HR Fourier spectrometer at the St. Petersburg site. Based on methodological studies of different spectral windows and regions, we show the possibility of determining 3–4 independent parameters of the CO₂ vertical structure. Measurements in strong and moderate absorption lines provide maximum information on the CO₂ content in the lower and middle troposphere with a vertical resolution of 3–5 km. Weak absorption lines provide information on the CO₂ content in the stratosphere with a vertical resolution of 10–25 km.

The results of studying spatial–temporal CO2variations near St. Petersburg in 2014–2017 based on satellite measurements (OCO-2 satellite) and ground-based spectroscopic and local...

Spectral line profiles are used to process experimental spectra when solving the inverse problem of computing the collisional parameters of the profiles [1]. The difference in their shapes is due to...

Doppler profiles of the Degenerate Resonant Four-Wave Mixing (DFWM) spectral responses from rapidly recoiling products of photodecomposition by plane-polarized radiation are theoretically studied. Emphasis is placed on the shapes produced by rotational helicity when orientations of the angular momenta and the recoil velocities of nascent particles are correlated. Illustrations are provided for cases when a decay of resonating states tangibly affects the helicity-induced DFWM profiles.

A weak, paradoxically narrow resonance feature (shortly, the r-line) near the O₂ fundamental frequency in the collision-induced absorption spectrum of oxygen dissolved in liquid argon and liquid nitrogen (T = 89 K) is resolved for the first time. An accurate band shape fitting routine to separate the r-line from the by-far more intense diffuse background and to study its behavior versus the oxygen mole fraction x which ranged from 0.03 up to 0.23 has been elaborated. At small x (≲0.07), the r-line intensity was found to scale as x² leaving no doubt that it is due to the solute-solute (O₂–O₂) interactions. In line with our results on the pH₂–LNe cryosystem [Herrebout, Phys. Rev. Lett. 101, 093001 (2008)], the Lorentzian r-line shape and its extraordinary sharpness (half width at half height ≈ 1 cm⁻¹) are indicative of the motional narrowing of the relative solute-solute translational spectrum. As x is further raised, ternary solute-solute interactions impede the r-line growth in the O₂–LAr spectrum because of the cancellation effect [J. Van Kranendonk, Physica 23, 825 (1957)]. Theoretical arguments are given that multiple interactions between the solutes should finally destroy the solute-solute induced r-line when the mixed solution approaches the limit of the pure liquid (x = 1). Interestingly, the nonbinary effects are too weak to appreciably affect the quadratic r-line scaling in the O₂–LN₂ cryosystem which persists up to x = 0.23. It is emphasized that studies of the resonant features in the collision-induced spectra of binary cryosolutions open up unique opportunities to spectroscopically trace the microscopic-scale diffusion.