Elena Jiménez

Elena Jiménez
University of Castilla-La Mancha · Departamento de Química-Física

Professor

About

86
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1,574
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October 2016 - March 2021
University of Castilla-La Mancha
Position
  • Professor (Full)

Publications

Publications (86)
Article
Full-text available
Saturated aldehydes, e.g. 2-methylbutanal (2 MB, CH3CH2CH(CH3)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2 MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms, and/or sunlight. In this work, we report the rate coefficients for the...
Article
Full-text available
Interstellar molecules containing N atoms, such as ammonia (NH 3 ) and methylamine (CH 3 NH 2 ), could be potential precursors of amino acids like the simplest one, glycine (NH 2 CH 2 COOH). The gas-phase reactivity of these N-bearing species with OH radicals, ubiquitous in the interstellar medium, is not known at temperatures of cold dark molecula...
Preprint
Full-text available
Saturated aldehydes, e.g. 2-methylbutanal (2MB, CH3CH2CH(CH3)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms and/or sunlight. In this work, we report the rate coefficients for the ga...
Article
Full-text available
The role of water vapor (H2O) and its hydrogen-bonded complexes in the gas-phase reactivity of organic compounds with hydroxyl (OH) radicals has been the subject of many recent studies. Contradictory effects have been reported at temperatures between 200 and 400 K. For the OH + acetaldehyde reaction, a slight catalytic effect of H2O was previously...
Article
Full-text available
The gas-phase reaction of trans-2-pentenal (T2P) with Cl atoms was studied at atmospheric pressure and room temperature. A rate coefficient of (2.56±0.83)×10-10 cm3 molecule-1 s-1 was obtained using the relative rate method and isoprene, cyclohexane and ethanol as reference compounds. The kinetic study was carried out using a 300-L Teflon bag simul...
Article
Gas-phase reactions in the interstellar medium (ISM) are a source of the molecules in this environment. The knowledge of the rate coefficient of neutral-neutral reactions as a function of temperature, k(T), is essential to improve the astrochemical models. In this work, we have experimentally measured k(T) for the reaction between the OH radical an...
Article
Full-text available
The gas-phase reaction between trans-2-methyl-2-butenal and chlorine (Cl) atoms has been studied in a simulation chamber at 298 ± 2 K and 760 ± 5 Torr of air under free-NOx conditions. The rate coefficient of this reaction was determined as k = (2.45 ± 0.32) × 10−10 cm3 molecule−1 s−1 by using a relative method and Fourier transform infrared spectr...
Article
Allyl cyanide, CH2CHCH2CN, is a volatile organic compound that is emitted by biogenic and anthropogenic sources. Daytime atmospheric degradation of CH2CHCH2CN may be initiated by reaction with OH radicals, Cl atoms and O3. In this work, we report the gas-phase rate coefficients for the reaction of these atmospheric oxidants with CH2CHCH2CN (k1, k2...
Article
The rate coefficient, k(T), for the gas-phase reaction between OH radicals and acetone CH3C(O)CH3, has been measured using the pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique (T = 11.7-64.4 K). The temperature dependence of k(T = 10-300 K) has also been computed using a RRKM-Master equation analysis after...
Article
The quantum dynamics of the title reactions are studied using the Ring Polymer Molecular Dynamics (RPMD) method from 20 to 1200 K using recently proposed full dimensional potential energy surfaces which include long range dipole-dipole interactions. A V-shaped dependence of the reaction rate constants is found with a minimum at 200-300 K, in rather...
Article
The rate coefficients, k ( T = 11.7 – 64.4 K), for the gas-phase reaction between OH radicals and acetone, CH 3 C(O) CH 3 , have been measured using the pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique, the most suitable one to cool down gases below the freezing point without gas condensation. The experimen...
Article
Full-text available
Methanol (CH 3 OH) and hydroxyl (OH) radicals are two species abundant in cold and dense molecular clouds which are important for the chemistry of the interstellar medium (ISM). CH 3 OH is a well-known starting point for the formation of more complex organic molecules (COMs) in these molecular clouds. Thus, the reactivity of CH 3 OH in the gas-phas...
Article
The reactivity of methanol (CH3OH) toward the hydroxyl (OH) radical was investigated in the temperature range 11.7 – 177.5 K using the CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique. In the present study, the temperature dependence of the rate coefficient for the OH+CH3OH reaction, k(T), has been revisited and a...
Article
The relative-rate technique has been used to determine the rate coefficient for the reaction of CxF2x+1CHCH2(x = 1, 2, 3, 4 and 6) with ozone at (298 ± 2) K and (720 ± 5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospher...
Article
The article “Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature” proposes a dimer mediated mechanism in order to explain the large low temperature rate coefficients for the OH + methanol reaction measured by several groups. It is demonstrated here theoretically that under the conditions of thes...
Article
Full-text available
Ethanol, CH3CH2OH, has been unveiled in the interstellar medium (ISM) by radioastronomy and it is thought to be released into the gas phase after the warm-up phase of the grain surface, where it is formed. Once in the gas phase, it can be destroyed by different reactions with atomic and radical species, such as hydroxyl (OH) radicals. The knowledge...
Article
The chemical kinetics of neutral–neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T ~ 10–100 K). Scarce kinetic information is currently available for these kinds of reactions at T < 200 K. In this work, we use...
Article
We report here the rate coefficients for the OH-reactions (kOH) with E-CF3CH=CHF and Z-CF3CH=CHF, potential substitutes of HFC-134a, as a function of temperature (263-358 K) and pressure (45-300 Torr) by pulsed laser photolysis coupled to laser induced fluorescence techniques. For the E-isomer, the existing discrepancy among previous results on the...
Article
A new method is proposed to represent analytically the potential energy surface of reactions involving polyatomic molecules capable to describe accurately long range interactions and saddle points, needed to describe low temperature collisions. It is based on two terms, a reactive force field term and a many body term. The reactive force field term...
Article
In many industrial applications, (CF3)2CFCN has been suggested as SF6 substitute, which possess a global warming potential (GWP100-yr) of 23500 relative to CO2. The temperature dependence of the rate coefficient (kOH) for the OH + (CF3)2CFCN reaction is reported for the first time: kOH(278–358 K) = (5.9 ± 3.2) × 10⁻¹³exp{−(1856 ± 162)/T} cm³ molecu...
Article
The interstellar medium attracts our great attention, as the place where stars and planets are born and from where, probably, the molecular precursors of life have come to Earth. To understand the chemical pathways to the formation of stars, planets, and biological molecules, astronomical observations, astrochemical modelling, and laboratory astroc...
Article
The interstellar medium attracts our great attention, as the place where stars and planets are born and from where, probably, the molecular precursors of life have come to Earth. To understand the chemical pathways to the formation of stars, planets, and biological molecules, astronomical observations, astrochemical modelling, and laboratory astroc...
Article
Rate coefficients for the gas-phase reactions of CxF2x+1CHCH2 (x = 1, 2, 3, 4 and 6) with Cl atoms were determined at (298 ± 2) K and (710 ± 5) Torr of air using a relative rate technique. Two experimental setups with simulation chambers were employed with Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography coupled to Mass Spectro...
Article
Full-text available
A series of three de Laval nozzles initially designed to generate uniform supersonic flows in helium at 23 and 36 K and in argon at 50 K have been used with either pure nitrogen or mixtures of nitrogen with helium or argon in order to make a sequence of pulsed supersonic flows working at different temperatures. For this, a computer homemade program...
Article
The GEISA database (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information) has been developed and maintained by the ARA/ABC(t) group at LMD since 1974. GEISA is constantly evolving, taking into account the best available spectroscopic data. This paper presents the 2015 relea...
Article
Full-text available
In the last years, ultra-low temperature chemical kinetic experiments have demonstrated that some gas-phase reactions are much faster than previously thought. One example is the reaction between OH and CH3OH, which has been recently found to be accelerated at low temperatures yielding CH3O as main product. This finding opened the question of whethe...
Article
Full-text available
In the last years, ultra-low temperature chemical kinetic experiments have demonstrated that some gas-phase reactions are much faster than previously thought. One example is the reaction between OH and CH3OH, which has been recently found to be accelerated at low temperatures yielding CH3O as main product. This finding opened the question of whethe...
Article
Hydrofluoroolefins (HFOs) of the type CF3(CF2)x≥0CHCH2, are currently being suggested as substitutes of some hydrofluorocarbons (HFCs). In this work, an assessment of the atmospheric removal of CF3(CF2)x=1,3,5CHCH2, initiated by reaction with hydroxyl (OH) radicals and UV solar radiation is addressed. For that purpose, the rate coefficients for the...
Article
The assessment of the atmospheric impact of the potential foam expansion agent, CF3(CF2)2CH=CH2 (HFC-1447fz), requires the knowledge of its degradation routes, oxidation products and radiative properties. In this paper, the gas-phase reactivity of HFC-1447fz with OH radicals is presented as a function of temperature, obtaining kOH(T=263-358K)=(7.4±...
Article
The gas phase chemistry of neutral-neutral reactions of interest in the interstellar medium (ISM) is poorly understood. The rate coefficients (kOH) for the majority of the reactions of hydroxyl (OH) radicals with interstellar oxygenated species are unknown at the temperatures of the ISM. In this study, we present the first determination of kOH for...
Article
A detailed description of a new pulsed supersonic uniform gas expansion system is presented together with the experimental validation of the setup by applying the CRESU (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow ) technique to the gas-phase reaction of OH radicals...
Article
Furanaldehydes, such as 2-furanaldehyde (also known as furfural), 3-furanaldehyde and 5-methyl-2-furanaldehyde, are aromatic aldehydes which can be present in the atmosphere as primary and secondary pollutants. The atmospheric removal initiated by sunlight for these species is not well-known in the solar actinic region (at λ > 290 nm), mainly due t...
Article
Full-text available
Atmospheric pollutants change our environment in a variety of ways. Specifically, airborne pollution is known to harm forests, crops, wildlife, aquatic ecosystems, and freshwater. In addition to damaging the natural environment, air pollution also affects buildings and the cultural material heritage such as outdoor sculptures and carvings.Direct ef...
Chapter
This chapter aims to review the daytime atmospheric chemistry of some carbonyl compounds, crucial intermediates in the autocatalytic production of the main atmospheric oxidant, the hydroxyl radical (OH•). Carbonyl compounds are very important trace gases for the physico-chemistry of the troposphere mainly because they are directly emitted into the...
Article
Full-text available
CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric l...
Article
As the result of biogenic and anthropogenic activities, large quantities of chemical compounds are emitted into the troposphere. Alkanes, in general, and cycloalkanes are an important chemical class of hydrocarbons found in diesel, jet and gasoline, vehicle exhaust emissions, and ambient air in urban areas. In general, the primary atmospheric fate...
Article
The relative importance in the atmosphere of UV photolysis of perfluoropropionaldehyde, CF3CF2CHO, and reaction with hydroxyl (OH) radicals has been investigated in this work. Firstly, the forbidden n-π* transition of the carbonyl chromophore was characterized between 230 and 380 nm as a function of temperature (269 - 298 K) and UV absorption cross...
Article
Three different detection techniques, coupled to pulsed laser photolysis (PLP), have been employed to determine the quantum yields of CF3CH2CHO at 248 and 266 nm: CF3CH2CHO + h nu -> CF3CH2 + HCO (R1a), CF3CH2CHO + h nu -> CF3CH3 + CO (R1b), and CF3CH2CHO + h nu -> CF3CH2O + H (R1c). (a) In the presence of air, Fourier transform infrared (FTIR) spe...
Article
The atmospheric reaction of the methylthiyl radical (CH3S) with O3 was investigated as a function of temperature (259–381 K), in the pressure range of 25–300 Torr, using the technique of laser photolysis/laser-induced fluorescence. The resulting Arrhenius expression, with an uncertainty of ±2σ, was k1(T=259–381 K)=(1.02±0.30)×10−12 exp[(432±77) K/T...
Article
An absolute kinetic study of the reaction of Cl atoms with CF3CF2CH2OH is reported as a function of temperature (T = 268–377 K) and at a total pressure of 100 Torr by the Pulsed Laser Photolysis - Resonance Fluorescence (PLP-RF) technique. No pressure dependence of the rate coefficient for the title reaction, k, was observed between 50 and 200 Torr...
Article
Relative kinetic techniques have been used to measure the rate coefficients for the reactions of oxygenated terpenes (menthol, borneol, fenchol, camphor, and fenchone) and cyclohexanol with hydroxyl radicals (OH) and chlorine atoms (Cl) at 298 ± 2 K and atmospheric pressure. The rate coefficients obtained for the reactions of the title compounds wi...
Article
This work constitutes the first study on the photochemical degradation process of CF3(CH2)2CHO. Firstly, the wavelength and temperature dependence of the UV absorption cross sections, σλ, was determined. The n → π* electronic transition band of CO chromophore was characterized between 230 and 340 nm in the 269–323 K range. A hyperchromic effect was...
Article
Fluorinated alcohols, such as 2,2,3,3-tetrafluoropropanol (TFPO, CHF(2)CF(2)CH(2)OH) and 2,2,3,3,3-pentafluoropropanol (PFPO, CF(3)CF(2)CH(2)OH), can be potential replacements of hydrofluorocarbons with large global warming potentials, GWPs. IR absorption cross sections for TFPO and PFPO were determined between 4000 and 500 cm(-1) at 298 K. Integra...
Article
Ultraviolet (UV) absorption cross sections of CF(3)CH(2)CHO were determined between 230 and 350 nm by gas-phase UV spectroscopy. The forbidden n → π* transition was characterized as a function of temperature (269-323 K). In addition, the photochemical degradation of CF(3)CH(2)CHO was investigated at 308 nm. The possible photolysis channels are: CF(...
Article
In the solar system, the temperature (T) of the atmosphere of giant planets or their satellites is only several tens of Kelvin (K). The temperature of the tropopause of Titan (satellite of Saturn) and the surface of Mars is 70 K and 210 K, respectively. In the Earth's atmosphere, T decreases from 298 K (surface) to 210 K close to the T-inversion re...
Article
The gas-phase kinetic coefficients of OH radicals with two primary fluorinated alcohols, CF(3)CH(2)CH(2)OH (k(1)) and CF(3)(CH(2))(2)CH(2)OH (k(2)), potential replacements of hydrofluorocarbons (HFCs), are reported here as a function of temperature (T = 263-358 K) for the first time. k(1) and k(2) (together referred as k(i)) were measured under pse...
Article
A comprehensive study of several atmospheric degradation routes for two hydrofluoroalcohols, CF(3)(CH(2))(x=1,2)CH(2)OH, is presented. The gas-phase kinetics of their reactions with hydroxyl radicals (OH) and chlorine (Cl) atoms are investigated by absolute and relative techniques, respectively. The room-temperature rate coefficients (±σ, in cm(3)...
Article
Relative rate coefficients for the gas-phase reaction of chlorine atoms (Cl) with tetrahydropyran (THP) have been determined by Fourier transform infrared (FTIR) spectroscopy and gas chromatography coupled to a mass spectrometer (GC–MS). The averaged rate coefficient is (2.21 ± 0.32) × 10−10 cm3 molecule−1 s−1 (with 2σ uncertainty) and was obtained...
Article
Full-text available
The absolute rate coefficients for the tropospheric reactions of chlorine (Cl) atoms and hydroxyl (OH) radicals with CF3CH2CHO and CF3(CH2)2CHO were measured as a function of temperature (263-371 K) and pressure (50-215 Torr of He) by pulsed UV laser photolysis techniques. Vacuum UV resonance fluorescence was employed to detect and monitor the time...
Article
Absolute rate coefficients for the gas-phase reactions of OH radical with 3-methylbutanal (k1), trans-2-methyl-2-butenal (k2), and 3-methyl-2-butenal (k3) have been obtained with the pulsed laser photolysis/laser-induced fluorescence technique. Gas-phase concentration of aldehydes was measured by UV absorption spectroscopy at 185 nm. Experiments we...
Article
An evaluation of the environmental impact of stressed-induced compounds, 1-penten-3-ol,(Z)-3-hexen-1-ol, and 1-penten-3-one (ethyl vinyl ketone, EVK), is presented in this paper. The removal processes considered here are the gas-phase reactions with hydroxyl (OH) radicals and photolysis in the actinic region (above 290 nm). The wavelength dependenc...
Article
Full-text available
The absolute rate coefficients for the tropospheric reactions of chlorine (Cl) atoms and hydroxyl (OH) radicals with CF3CH2CHO and CF3(CH2)2CHO were measured as a function of temperature (263–371 K) and pressure (50–215 Torr of He) by pulsed UV laser photolysis techniques. Vacuum UV resonance fluorescence was employed to detect and monitor the time...
Article
UV absorption cross sections (σλ) for 3-methylbutanal, trans-2-methyl-2-butenal, and 3-methyl-2-butenal have been determined between 255 and 390nm and as a function of temperature (273–305K). A D2 lamp and a 0.5m spectrograph coupled to a charged-couple device were employed in these measurements. σλ values were found to be independent of temperatur...
Article
A newly constructed chamber/Fourier transform infrared system was used to determine the relative rate coefficient, k(i), for the gas-phase reaction of Cl atoms with 2-butanol (k(1)), 2-methyl-2-butanol (k(2)), 3-methyl-2-butanol (k(3)), 2,3-dimethyl-2-butanol (k(4)) and 2-pentanol (k(5)). Experiments were performed at (298 +/- 2) K, in 740 Torr tot...
Article
Full-text available
The ultraviolet (lambda=250-370 nm) photolysis and the OH-initiated oxidation of hexanal and trans-2-hexenal, which are relevant atmospheric processes, have been investigated at room temperature and as a function of temperature (T=263-353 K), respectively. This kinetic study as a function of temperature is reported here for the first time. Absolute...
Article
The ultraviolet (λ=250–370 nm) photolysis and the OH-initiated oxidation of hexanal and trans-2-hexenal, which are relevant atmospheric processes, have been investigated at room temperature and as a function of temperature (T=263–353 K), respectively. This kinetic study as a function of temperature is reported here for the first time. Absolute abso...
Article
The absolute rate coefficients for the reactions of hydroxyl radical (OH) with 2-butanol (k(1)), 2-methyl-2-butanol (k(2)), and 2,3-dimethyl-2-butanol (k(3)) were measured as a function of temperature (263-354 K) and pressure (41-193 Torr of He, Ar, and N(2)) by the pulsed laser photolysis/laser-induced fluorescence technique. This work represents...
Article
Quantum yields, phi, of OH and HO2 in the ultraviolet photolysis of HO2NO2 (peroxynitric acid, PNA) at 193 and 248 nm and that of NO3 at 193, 248 and 308 nm are reported. Quantum yields were measured using pulsed excimer laser photolysis combined with pulsed laser induced fluorescence (PLIF) detection of OH radicals and cavity ring-down (CRD) detec...
Article
The reactions of chlorine (Cl) atoms with volatile organic compounds (VOCs) emitted into the atmosphere are of interest to understand the role of Cl in the marine and coastal chemistry. The rate coefficients for Cl-atom reactions with organic compounds are typically about one or two order of magnitude larger than the ones corresponding to OH reacti...
Article
Rate coefficients for the gas-phase thermal decomposition of HO(2)NO(2) (peroxynitric acid, PNA) are reported at temperatures between 331 and 350 K at total pressures of 25 and 50 Torr of N(2). Rate coefficients were determined by measuring the steady-state OH concentration in a mixture of known concentrations of HO(2)NO(2) and NO. The measured the...
Article
The absolute rate coefficients for the tropospheric reactions of hydroxyl radical (OH) with a series of linear aliphatic ketones (2-butanone (k1), 2-pentanone (k2), 2-hexanone (k3), and 2-heptanone (k4)) were measured as a function of temperature (228-405 K) and pressure (45-600 Torr of He) by the pulsed laser photolysis/laser induced fluorescence...
Article
Rate coefficients (k3(T)) for the reaction of OH with HO2NO2 (peroxynitric acid, PNA) in the gas phase were measured in the temperature range of 218−335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H2O2, HNO3, and NO2 impurities...
Article
Absolute rate coefficients for the reactions of OH radical (kOH) with 3-fluoropropene, 3-chloropropene, 3-bromopropene, and 3-iodopropene were determined as a function of the total pressure (pT =100–600Torr) and the temperature (228–388K) using the pulsed laser photolysis/laser-induced fluorescence technique. No significant pressure dependence of r...