Toward non-invasive measurement of atmospheric temperature using vibro-rotational raman spectra of diatomic gases

We demonstrate precise determination of atmospheric temperature using vibro-rotational Raman (VRR) spectra of molecular nitrogen and oxygen in the range of 292–293 K. We used a continuous wave fiber laser operating at 10 W near 532 nm as an excitation source in conjunction with a multi-pass cell. First, we show that the approximation that nitrogen and oxygen molecules behave like rigid rotors leads to erroneous derivations of temperature values from VRR spectra. Then, we account for molecular non-rigidity and compare four different methods for the determination of air temperature. Each method requires no temperature calibration. The first method involves fitting the intensity of individual lines within the same branch to their respective transition energies. We also infer temperature by taking ratios of two isolated VRR lines; first from two lines of the same branch, and then one line from the S-branch and one from the O-branch. Finally, we take ratios of groups of lines. Comparing these methods, we found that a precision up to 0.1 K is possible. In the case of O2, a comparison between the different methods show that the inferred temperature was self-consistent to within 1 K. The temperature inferred from N2 differed by as much as 3 K depending on which VRR branch was used. Here we discuss the advantages and disadvantages of each method. Our methods can be extended to the development of instrumentation capable of non-invasive monitoring of gas temperature with broad potential applications, for example, in laboratory, ground-based, or airborne remote sensing

Minimally invasive spleen-preserving distal pancreatectomy: real-world data from the italian national registry of minimally invasive pancreatic surgery

Aim: Minimally invasive distal pancreatectomy has become the standard of care for benign and low malignant lesions. Spleen preservation in this setting has been proposed to reduce surgical trauma and long-term sequelae. The aim of the current study is to present real-world data on indications, techniques, and outcomes of spleen-preserving distal pancreatectomy (SPDP). Methods: Patients who underwent SPDP and distal pancreatectomy with splenectomy (DPWS) were extracted from the 2019-2022 Italian National Registry for Minimally Invasive Pancreatic Surgery (IGoMIPS). Perioperative and pathological data were collected. Results: One hundred and ten patients underwent SPDP and five hundred and seventy-eight underwent DPWS. Patients undergoing SPDP were significantly younger (56 vs. 63.5 years; P < 0.001). Seventy-six percent of SPDP cases were performed in six out of thirty-four IGoMIPS centers. SPDP was performed predominantly for Neuroendocrine Tumors (43.6% vs.23.5%; P < 0.001) and for smaller lesions (T1 57.6% vs. 29.8%; P < 0.001). The conversion rate was higher in the case of DPWS (7.6% vs. 0.9%; P = 0.006), even when pancreatic cancer was ruled out (5.0% vs. 0.9%; P = 0.045). The robotic approach was most commonly used for SPDP (50.9% vs. 29.7%; P < 0.001). No difference in postoperative outcomes and length of stay was observed between the two groups, as well as between robotic and laparoscopic approaches in the SPDP group. A trend toward a lower rate of postoperative sepsis was observed after SPDP (0.9% vs. 5.2%; P = 0.056). In 84.7% of SPDP, splenic vessels were preserved (Kimura procedure) without an impact on short-term postoperative outcomes. Conclusion: In this registry analysis, SPDP was feasible and safe. The Kimura procedure was prevalent over the Warshaw procedure. The typical patient undergoing SPDP was young with a neuroendocrine tumor at an early stage. Robotic assistance was used more frequently for SPDP than for DPWS

Effects of anisotropic interaction on collision-induced absorption by pairs of linear molecules

Calculations of collision-induced absorption spectral moments 1 and 1 for N2 and CO2 molecular pairs are presented which, for the first time, fully account for the anisotropic components of the intermolecular potentials. The results of these rigorous computations, performed at selected temperatures, are compared with approximations based on the perturbative approach and the infinite-order sudden approximation. In this way both important aspects of the effects of an anisotropic interaction and the ability of these two approximations to take them into account are demonstrated. © 1992 The American Physical Society

Effects of the intermolecular interaction on the depolarized rototranslational Raman spectra of hydrogen

Calculations of the rotational Raman spectra of hydrogen at high gas densities and various temperatures are presented. Both the far wings and the line cores are considered where collisional induction and pressure broadening shape the profiles. The treatment of far wings follows previous calculations which had given encouraging results. In the present work, new components of the collision-induced polarizability have been considered in an attempt to remove the previously observed inconsistencies with existing measurements. The far-wing spectral intensities and the Raman linewidths are computed by using two different intermolecular potentials. It is shown that Raman linewidths are more sensitive to the details of the intermolecular potential than far-wing Raman intensities. Comparison with experimental data does not allow one to determine which of the two potentials is to be preferred over the other. © 1993 The American Physical Society

The role of the anisotropic interaction on collision induced absorption of systems containing linear molecules: The CO \u3c inf\u3e 2 -Ar case

Numerical calculations are presented of spectral moments of collision induced absorption (CIA) coefficient of CO2-Ar mixtures at various temperatures. Three spherical components have been used for the induced dipole moment all of which arise from pure multipolar induction. The calculations have been performed with six different potentials which differ with respect to the amount of anisotropy. The comparison of experimental and numerical results shows that the potential proposed by Preston and Pack [J. Chem. Phys. 66, 2480 (1977)] is the most suitable to describe CIA spectra. In addition, it is shown that the role of the anisotropy of the potential with regard to its contribution to the spectral moments, particularly the amount of mixing of dipole components of different symmetry, cannot be neglected. © 1993 American Institute of Physics

Research note on the symmetrization of rotational spectra for freely rotating linear molecules

It is demonstrated that the symmetrization of a quantum mechanical rotational spectrum of freely rotating linear molecules by means of the Egelstaff transformation produces a symmetric spectrum whose first two even moments coincide with the corresponding classical moments. © Taylor & Francis Group, LLC

On the interpretation of the Q-branch of hydrogen in water

© 2016 IOP Publishing Ltd. The Raman Q branch of hydrogen dissolved in water is interpreted by means of a theory based on perturbative methods. Consistent with experimental results on pure rotational lines, in the theory we assume that the shifts of the lines composing the Q branch do not depend on the rotational states. It is found that an important mechanism determining the structure of the Q branch is the motional narrowing effect, particularly for the transitions involving ortho-hydrogen. A simple model of the Q branch allows the estimation of the rotational and vibrational relaxation properties of hydrogen in solution with water

Rotational lines of hydrogen in water

In this paper we report new calculations of the shape of the Raman rotational lines of hydrogen in solution with water. The method was based on a perturbative treatment and the calculations were performed for a system at room temperature and pressure ≈14 MPa, a thermodynamic state at which both measurements and accurate non-adiabatic calculations were available. The scope of the paper is to compare our numerical findings both with the computational results obtained with the non-adiabatic method and with the measured widths of the rotational lines. We found that our results are very similar to those obtained with the non-adiabatic method. Calculations of the widths were made with different models for the hydrogen–water intermolecular potential. The comparison of the numerical evaluations with the experimental findings allows us to judge how dependable the potential models are. The same calculations were performed also at larger pressures, up to 160 MPa. It was found that the widths of the rotational lines increased by increasing the pressure whereas, at the same pressure, they decreased when the rotational quantum number of the initial state was increased