The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples, a cometary origin was deduced from the 13C isotopic signature. We report the presence of volatile glycine accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result demonstrates that comets could have played a crucial role in the emergence of life on Earth.

https://advances.sciencemag.org/content/advances/2/5/e1600285.full.pdf

Prebiotic chemicals—amino acid and phosphorus—in the coma of comet 67P/Churyumov-Gerasimenko

A detailed global model of atmospheric-pressure He + H2O plasmas is presented in this paper. The model incorporates 46 species and 577 reactions. Based on simulation results obtained with this comprehensive model, the main species and reactions are identified, and simplified models capable of capturing the main physicochemical processes in He + H2O discharges are suggested. The accuracy of the simplified models is quantified and assessed for changes in water concentration, input power and electrode configuration. Simplified models can reduce the number of reactions by a factor of similar to 10 while providing results that are within a factor of two of the detailed model. The simulation results indicate that Penning processes are the main ionization mechanism in this kind of discharge (1-3000 ppm of water), and water clusters of growing size are found to be the dominant charged species when the water concentration is above similar to 100 ppm. Simulation results also predict a growing electronegative character of the discharge with increasing water concentration. The use of He + H2O discharges for the generation of reactive oxygen species of interest in biomedical applications and the green production of hydrogen peroxide are also discussed. Although it would be unrealistic to draw conclusions regarding the efficacy of these processes from a zero-dimensional global model, the results indicate the potential suitability of He + H2O plasmas for these two applications.

https://iopscience.iop.org/article/10.1088/0963-0252/19/2/025018/pdf

Global model of low-temperature atmospheric-pressure He + H2O plasmas

Electron–molecule collision calculations using the R-matrix method

Combustion of butanol isomers – A detailed molecular beam mass spectrometry investigation of their flame chemistry

Entanglement is nowadays considered as a key quantity for the understanding of correlations, transport properties and phase transitions in composite quantum systems, and thus receives interest beyond the engineered applications in the focus of quantum information science. We review recent experimental and theoretical progress in the study of quantum correlations under that wider perspective, with an emphasis on rigorous definitions of the entanglement of identical particles, and on entanglement studies in atoms and molecules.Corrections were made to this article on 28 September 2011. The received date was incorrectly given.

https://iopscience.iop.org/article/10.1088/0953-4075/44/19/192001/pdf

Essential entanglement for atomic and molecular physics

Various total cross sections for collisions of electrons in the energy range 10--2000 eV are calculated for the tetrahedral ${\mathrm{CH}}_{4},$ ${\mathrm{SiH}}_{4},$ ${\mathrm{GeH}}_{4},$ ${\mathrm{CF}}_{4},$ ${\mathrm{SiF}}_{4},$ and ${\mathrm{CCl}}_{4}$ targets and ${\mathrm{SF}}_{6}.$ Molecular total inelastic cross sections determined in the complex potential formalism are partitioned to account for the ionization and cumulative electronic-excitation channels. The present total cross sections and total ionization cross sections are found to be consistent with the previous data. The cumulative total excitation cross sections reported here indicate the relative importance of ionization together with electronic excitation channels including neutral dissociation of these molecules by electron impact.

Calculated total cross sections of electron-impact ionization and excitations in tetrahedral (XY~4) and SF~6 molecules (6 pages)

Various total cross sections for the impact of electrons on free radicals CHx ,N Hx and OH are calculated at intermediate to high energies. The known ionization data on the parent molecules CH4 ,N H 3 and H2O are employed to extract total ionization cross sections of the respective radicals using total inelastic cross sections, which we have calculated through a complex optical potential. The results give an upper bound of the total ionization cross section in the energy region around 100 eV, and are in suitable harmony with available experimental data at higher energies.

https://iopscience.iop.org/article/10.1088/0953-4075/34/4/301/pdf

Electron impact total cross sections of CHx ,N H x and OH radicals vis-` a-vis their parent molecules

Electron impact total (50 to 2000 eV) and ionization
(threshold to 2000 eV) cross-sections are calculated using the
SCOP and CSP-ic methods [Phys. Rev. A 69, 022705 (2004)]
for the hydrocarbon molecules (CH4, C2H2, C2H4,
C2H6, C3H4, C3H6 and C3H8) and radicals
(CHx (x=1-3)). Present method has already been tested
successfully to many other aeronomic [Int. J. Mass Spectrom.
233, 207 (2004)] and plasma molecules and radicals. Our
results exhibited in this paper show good agreement with
experimental results where available. For the radical species, we
have presently done a first estimate of the total cross-sections.

Electron impact total and ionization cross-sections for some hydrocarbon molecules and radicals

Total cross sections (TCSs) including ionization cross sections for the impact of intermediate and high energy electrons on ozone as well as O, O2 and O4 targets are calculated and compared with available measurements. The calculation proceeds through a complex energy-dependent potential derived from the atomic/molecular electron charge density. The summed total inelastic cross sections determined in this formalism are used to derive total ionization cross sections Qion, as done in our recent work on many other atomic and molecular targets. The present TCS results show good accord with the recent experimental data on e–O3 scattering, but the corresponding ionization results favour the available theoretical rather than the experimental data. Our results on atomic and molecular oxygen show good accord with previous investigations of other workers. Preliminary estimates on O4 are also given.

https://iopscience.iop.org/article/10.1088/0953-4075/35/20/308/pdf

Electron scattering and ionization of ozone, O2 and O4 molecules

In this paper we report comprehensive calculations of total elastic (Qel), total ionization (Qion) and total (complete) cross sections (QT) for the impact of electrons on inert gases (He, Ne, Ar, Kr and Xe) at energies from about threshold to 2000 eV. We have employed the spherical complex optical potential (SCOP) formalism to evaluate Qel and QT and used the complex spherical potential-ionization contribution (CSP-ic) method to derive Qion. The dependence of QT on polarizability and incident energy is presented for these targets through an analytical formula. Mutual comparison of various cross sections is provided to show their relative contribution to the total cross sections QT. Comparison of QT for all these targets is carried out to present a general theoretical picture of collision processes. The present calculations also provide information, hitherto sparse, on the excitation processes of these atomic targets. These results are compared with available experimental and other theoretical data and overall good agreement is observed.

K. N. Joshipura

Papers

Calculated total cross sections of electron-impact ionization and excitations in tetrahedral (XY~4) and SF~6 molecules (6 pages)

Electron impact total cross sections of CHx ,N H x and OH radicals vis-` a-vis their parent molecules

Electron impact total and ionization cross-sections for some hydrocarbon molecules and radicals

Electron scattering and ionization of ozone, O2 and O4 molecules

Calculations of elastic, ionization and total cross sections for inert gases upon electron impact: threshold to 2 keV