J. Wnorowska

Bio: J. Wnorowska is an academic researcher. The author has contributed to research in topics: Electron capture & Ion. The author has an hindex of 6, co-authored 12 publications receiving 94 citations.

Low-Energy Electron Attachment by Chloroalkanes

Abstract: Thermal electron attachment rate constants for 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1- and 2-chloropropanes, and 1,1-, 1,2-, 2,2-, and 1,3-dichloropropanes have been measured using an electron swarm method. It has been found that all the investigated compounds attach electrons only in a two-body process. Corresponding rate constants are equal to 1.4 x 10 - 1 0 , 3.2 x 10 - 8 , 2.7 × 10 - 1 3 , 3.8 × 10 - 1 2 , 5.7 × 10 - 1 1 , 8.1 × 10 - 1 2 , 6.3 × 10 - 1 2 , and 1.2 x 10 - 1 1 cm 3 molecule - 1 s - 1 , respectively. The dependence of the electron capture rate constants on the electronic polarizability of the accepting center of the molecule and the vertical attachment energy has been demonstrated.

A new apparatus for measuring rate constants and activation energies of thermal electron capture processes in the gas phase

Abstract: The new apparatus for investigation of kinetics of a thermal electron capture process and its temperature dependence with pulsed Townsend technique has been built. This method gives straightforward results on electron drift velocities in any mixture and allows calculating the rate constants for electron capture as well as activation energies of this process. The thermal electron capture rate constants and activation energies for CH3CCl3, CHCl2CH2Cl and CH3CHClCH2CH3 have been determined.

Low energy electron attachment by bromoalkanes

Abstract: Electron attachment process in three halopropanes, CH3CH2CH2Br, CH3CHBrCH3 and CH3CHBrCF3, have been investigated using an electron swarm and electron capture negation mass spectrometry techniques. All compounds attach electrons in dissociative process, and the main product is bromine ion. The rate constants for thermal electron attachment are equal to 1.1·10−1, 1.4·10−12 and 4.1·10−10 cm3molec.−1 s−1 for CH3CH2CH2Br, CH3CHBrCH3 and CH3CHBrCF3, respectively.

Electron attachment to oxygen in nitrogen buffer gas at atmospheric pressure

Abstract: We have carried out experimental and theoretical studies of three body electron attachment (TBEA) to O2 in N2/O2 mixtures. We have applied three different experimental methods to determine the apparent rate constant k for TBEA to O2 for reduced electric fields E/ n from 0.5 Td up to 4.5 Td and O2 concentrations from 0.02% up to 3%. From the apparent rate constant k we have evaluated three body rate constant for electron attachment to O2 in pure O2 $$\left( {k_{O_2 } } \right)$$ and in pure N2 $$\left( {k_{N_2 } } \right)$$ . The comparison of present data with former studies shows that the former values of $$k_{N_2 }$$ overestimated the efficiency of this reaction, while in case of $$k_{O_2 }$$ we have found agreement with earlier studies. We have solved numerically the Boltzmann equation of the electrons and calculated the values of k, $$k_{N_2 }$$ and $$k_{O_2 }$$ using well established cross sections. Using the known collision cross section set for TBEA to O2, very good agreement between calculated and measured results for $$k_{O_2 }$$ was found, while in the case of k and $$k_{N_2 }$$ we had to introduce a scaling function, which describes the decrease of the efficiency of TBEA to O2 in presence of N2 and the dependence of the scaling function on E/n was determined.

The influence of the temperature on electron attachment to some halocontaining molecules

Abstract: Thermal electron attachment rate coefficients for CH 2 ClCHClCH 2 Cl, CH 2 ClCH 2 Br, CH 2 ClCH 2 CH 2 Br and CF 2 ClCFCl 2 have been measured using the Pulsed Townsend technique over the temperature range T = 298–358 K. The corresponding rate coefficients at 298 K are equal to 1.7(4) × 10 −10 , 7.9(15) × 10 −10 , 3.4(5) × 10 −10 and 3.1(1) × 10 −8 cm 3 molec. −1 s −1 , respectively. With rising temperature we have observed an increase of the rate coefficients k ( T ), which shows an Arrhenius-type behaviour. Activation energies E a of 0.16(1) eV (CH 2 ClCHClCH 2 Cl), 0.12(1) eV (CH 2 ClCH 2 Br), 0.20(1) eV (CH 2 ClCH 2 CH 2 Br) and 0.08(1) eV (CF 2 ClCFCl 2 ) were determined from the fit to the experimental data points with a function ln( k ) = ln( A ) − E a / k B T .

Recent Progress in Dissociative Electron Attachment: From Diatomics to Biomolecules

Abstract: Dissociative electron attachment (DEA) processes occur in many important applied contexts, particularly gas discharges, plasmas, biological systems, and astrophysical environments. In this review, we survey the basic physics of DEA and the progress that has been made during past 14 years since the last important review on DEA (Hotop et al., Adv. At. Mol. Opt. Phys. 49, 86). This progress includes studies of DEA to simple diatomic and polyatomic molecules with high energy resolution revealing vibrational Feshbach resonances and threshold structures, studies of angular distribution of the fragmentation products allowing analysis of the symmetries of the resonances involved, and theoretical developments in investigating the dynamics of nuclear motion in DEA processes. Particular attention is paid to recent advances in DEA to biological molecules as the process is important for understanding radiation damage. Recent progress in understanding electron attachment to van der Waals clusters and the influence of cluster environments on DEA is also reviewed. The review concludes with a forward look and suggestions for new research directions.

High-resolution electron attachment to the molecules CCl4 and SF6 over extended energy ranges with the (EX)LPA method

Abstract: Using a variant of the laser photoelectron attachment (LPA) method with an extended energy range (EXLPA), we have studied low-energy electron attachment to the molecules CCl4 (Cl− and Cl−2 formation) and SF6 (SF−6 and SF−5 formation) in a diffuse gas target (TG = 300 K) from 0 eV up to 2 eV at energy widths down to 14 meV. In the EXLPA method, pulses of near-zero energy photoelectrons are produced in a guiding magnetic field, accelerated by a weak electric field, brought to the energy of interest prior to their traversal through the target region and subsequently accelerated and deflected onto a detecting plate. Anions due to electron attachment are extracted by a pulsed electric field, during which the photoelectron current is interrupted, and detected by a quadrupole mass spectrometer. The EXLPA anion yields are combined with absolute cross sections, obtained at very high resolution (≈1 meV) with the LPA method over the range 0–0.17 eV, to yield new recommended absolute partial and total attachment cross sections over the range 0–2 eV at the well-defined gas temperature TG = 300 K. Our cross sections show characteristic deviations from previously reported results. At least in part, these differences can be attributed to the fact that in the earlier electron beam experiments the gas temperature was higher than 300 K. For SF6, the branching fractions for SF−5 formation at electron energies 0.002–0.43 eV and for different initial rovibrational distributions are compared with those recently predicted from kinetic modelling within the framework of statistical unimolecular rate theory. Satisfactory agreement is observed, but our data provide evidence that an additional path for producing SF−6 and SF−5 ions is available at electron energies above about 0.3 eV.

Thermal Electron Attachment and Detachment in Gases

Abstract: This article describes measurements of electron attachment and detachment rate constants made in the thermal environment of a flowing-afterglow Langmuir-probe apparatus (FALP) at the Air Force Research Laboratory (AFRL). If the molecular electron affinity is low enough that electron detachment from the parent anion occurs in the temperature range of the apparatus (298–550 K), the attachment/detachment equilibrium constant allows accurate determination of the electron affinity. Electron attachment reactions to a variety of molecules is described, from simple hexafluorides to transition-metal trifluorophosphines and carbonyls.

Measurements of thermal electron attachment rate coefficients to molecules using an electron swarm technique

Abstract: An existing electron swarm apparatus has been redesigned and upgraded. In particular, the new design incorporates a novel planar radioactive foil to form an integral part of the drift tube, allowing us to overcome inherent problems present in our earlier system which used a cylindrical radioactive source. In addition to this, substantial upgrades have been made to improve the gating and amplification electronics and the data acquisition system. This has resulted in a much greater signal to noise ratio and improved accuracy. This paper describes the upgraded apparatus and its use in obtaining thermal (300 K) attachment rate coefficients to a number of molecules. The quality of the measurements and data are illustrated through the measurement of the thermal attachment rate coefficient for SF6 (kth(SF6) = (2.38 ±0.15 ) ×10 -7 cm3 s-1). Thermal electron attachment rate coefficients for four other molecules are presented, namely for two derivatives of SF6, SF5CF3 and SF5Cl, and two perfluorocarbons, c-C4F8 and 2-C4F8.

An Efficient Procedure to Identify and Quantify New Molecules for Insulating Gas Mixtures

Abstract: In this contribution, a new procedure to systematically identify and quantify novel molecular gases with low global warming potential for application in high voltage insulation as gas mixtures is presented. The attention is focused on highly efficient procedures to be able to scan a large number of candidate gases. To identify new molecules, we derived an empirical correlation between the electric strength of a gas and certain molecular properties, like polarizability or dipole moment, which can be calculated by means of density functional theory. The swarm parameters of these pre-selected molecules in mixtures with buffer gases is then quantified, using a newly set-up Pulsed Townsend experiment. The setup operates with a high degree of automation to enable systematic evaluation of gas mixtures not to miss possible synergistic effects. Key element of this PT setup is a new photocathode that works with a high quantum efficiency and long lifetime even when exposed to reactive species during the measurements. Moreover, for an automated operation it is important to know precisely in which range the experiment can be operated, i.e. for example to know up to which electron density space charge effects can be neglected. Finally, the measured swarm parameters need to be translated into breakdown voltage strengths of different electrode arrangements and different applied voltage wave shapes. For this, a model of the the streamer to leader transition in SF6 will be applied to other strong electronegative gases in future studies to test if the model is universally valid. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)