Ab Initio Calculation Applied To The Study Of Organic Non-rigid Molecules With (at Least) Three Torsional Modes

Methods applicable to the spectroscopic study of non-rigid organic molecular species with various large amplitude motions (torsions and inversions), are shown. Recent studies of ethylene glycol, \chem{C_3O_6H_6} isomers, and other species containing C, H, O, and N are employed as examples. Many organic molecules display non-rigidity. Vibrational modes (inversions and torsions) interconvert different conformers separated by relatively low barriers. Some conformers can be stabilized by the presence of hydrogen intermolecular bonds that can determine their geometry, symmetry, the shape of the potential energy surface and the internal dynamics. When a species displays three or more large amplitude motions, which cannot be separated because they interact strongly, the variational calculation of vibrational levels is complex and requires to search for ways reducing computational efforts. Especially tricky is the classification of the vibrational levels and their splittings

A new Unidentified Far Infrared Band in NGC7027

We report on the detection of a molecular band centered at ~98 um (~102 cm^-1), observed with the Infrared Space Observatory in the young Planetary Nebula NGC7027. The band structure and intensity can not be reproduced by atomic fine structure lines, recombination lines or by the rotational emission of abundant molecules. We discuss the possible contribution of the low-energy bending modes of pure carbon chains to the unidentified far-IR bands (UfIBs) observed in C-rich evolved objects. In particular, we speculate that the band emission could arise from the nu_9 and nu_7 bending modes of C_6 and C_5, for which wavenumbers of 90+/-50 and 107+/-5 cm^-1 have been estimated from photoelectron spectroscopy.Comment: 15 pages, 2 figures, accepted in ApJ part

Weak intramolecular interactions effcts on the structure and the torsional spectra of ethylene glycol, an astrophysical species

A variational procedure of reduced dimensionality based on CCSD(T)-F12 calculations is applied to understand the far infrared spectrum of Ethylene-Glycol. This molecule can be classified in the double molecular symmetry group G8 and displays nine stable conformers, gauche and trans. In the gauche region, the effect of the potential energy surface anisotropy due to the formation of intramolecular hydrogen bonds is relevant. For the primary conformer, the ground vibrational state rotational constants are computed at 6.3 MHz, 7.2 MHz and 3.5 MHz from the experimental parameters. Ethylene glycol displays very low torsional energy levels whose classification is not straightforward. Given the anisotropy, tunneling splittings are significant and unpredictable. The ground vibrational state splits into 16 sublevels separated approximately 142 $cm^{-1}$. Transitions corresponding to the three internal rotation modes allow assign previous observed Q branches. Band patterns, calculated between 362.3 $cm^{-1}$ and 375.2 $cm^{-1}$, between 504 $cm^{-1}$ and 517 $cm^{-1}$ and between 223.3 $cm^{-1}$ and 224.1 $cm^{-1}$, that correspond to the tunnelling components of the v21 fundamental ($\nu_{21}$ = OH-torsional mode), are assigned to the prominent experimental Q branches

Molecules as Diagnostic Tools in the Interstellar Medium

International audienceAnalysis of light emission from different regions of the interstellar medium and circumstellar environments gives crucial information about the chemical composition and the physical conditions in these regions. Interpretation of the observed spectra requires the knowledge of collisional excitation rates as well as radiative rates participating to the line formation. In a first part, this paper focuses on collisional excitation rates of molecules relevant to the interstellar medium. It discusses currently available data and outlines new work carried out by the authors. Due to the use of accurate ab initio potential energy surfaces, the new rate coefficients differ significantly from previously published ones. In a second part, the paper analyses from two examples how the use of the new rates could lead to important changes in the interpretation of molecular emission emerging from molecular clouds

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Sin / Sense

Sexto desafío por la erradicación de la violencia contra las mujeres del Institut Universitari d’Estudis Feministes i de Gènere «Purificación Escribano» de la Universitat Jaume

DIMETHYL ETHER THREE DIMENTIONAL SPECTRA

Author Institution: Departamento de Quimica. Universidad Autonoma Metropolitana, Av. San Rafael Atlixco 186, Col Vicentina, Iztapala, Mexico D.F. 09340, MEXICO; Departamento de Astrofisica Molecular e Infrarroja, Instituto de Estructura de la Materia, C.S.I.C., Serrano 113B, Madrid 28006, SPAINThe dimethyl ether is a non-rigid molecule with three internal motions: the two methyl rotations and the COC bending. This motions are studied using MP2 and CCSD(T) calculations using a aug-cc-pVTZ basis set and applying the ZPVE corrections. With these results the 3D spectra is calculated

XXVII Jornadas Chilenas de Química

International audienc