Martin Ferus

High-energy chemistry of formamide: A unified mechanism of nucleobase formation

Significance This paper addresses one of the central problems of the origin of life research, i.e., the scenario suggesting extraterrestrial impact as the source of biogenic molecules. Likewise, the results might be relevant in the search of biogenic molecules in the universe. The work is therefore highly actual and interdisciplinary. It could be interesting for a very broad readership, from physical and organic chemists to synthetic biologists and specialists in astrobiology. The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules.

On the Road from Formamide Ices to Nucleobases: IR-Spectroscopic Observation of a Direct Reaction between Cyano Radicals and Formamide in a High-Energy Impact Event

The formamide-based synthesis of nucleic acids is considered as a nonaqueous scenario for the emergence of biomolecules from inorganic matter. In the current study, we scrutinized the chemical composition of formamide ices mixed with an FeNi meteorite material treated with laser-induced dielectric breakdown plasma created in nitrogen buffer gas. These experiments aimed to capture the first steps of those chemical transformations that may lead to the formation of nucleobases during the impact of an extraterrestrial icy body containing formamide on an early Earth atmosphere. High-resolution FT-IR spectroscopy combined with quantum chemical calculations was used to analyze the volatile fraction of the products formed during such an event. We have found that the spectrum of the evaporated formamide ices is dominated by the spectral signatures of the dimeric form of formamide. Upon exposure to laser sparks, new well-defined bands appear in the spectrum centered at ~820, ~995, and ~1650 cm(-1). On the basis of quantum chemical calculations, these bands can be assigned to the absorptions of 2-amino-2-hydroxy-acetonitrile and to 2-amino-2-hydroxy-malononitrile, which are formed in a direct reaction between formamide and CN(•) radicals upon the high-energy impact event. We also show that there is an exergonic reaction route via these intermediates leading to diaminomaleonitrile, which is generally considered to play a key role in the synthesis of nucleobases.

Oxygen-isotope labeled titania: Ti18O2

(18)O-isotope labelled titania (anatase, rutile) was synthesized. The products were characterized by Raman spectra together with their quantum chemical modelling. The interaction with carbon dioxide was investigated using high-resolution FTIR spectroscopy, and the oxygen isotope exchange at the Ti(18)O(2)/C(16)O(2) interface was elucidated.

High-Energy Chemistry of Formamide: A Simpler Way for Nucleobase Formation

The formation of nucleobases from formamide during a high-energy density event, i.e., the impact of an extraterrestrial body into the planetary atmosphere, was studied by irradiation of formamide ice and liquid samples with a high-power laser in the presence of potential catalysts. FTIR spectroscopy, time-resolved emission spectroscopy, and GC-MS were subsequently used to monitor the dissociation of this molecule into stable molecular fragments (HCN, H2O, HNCO, H2, CO, and NH3) and unstable species (HNC, •CN, and •NH). The kinetic and thermodynamic models of the high-energy density event molecular dynamics have been suggested together with the reaction routes leading from the dissociation products to the nucleobases. In addition, using theoretical calculations, we propose a simple new reaction pathway for the formation of both pyrimidine and purine nucleobases involving •CN radical chemistry.

HNC/HCN ratio in acetonitrile, formamide, and BrCN discharge.

Time-resolved Fourier transform (FT) spectrometry was used to study the dynamics of radical reactions forming the HCN and HNC isomers in pulsed glow discharges through vapors of BrCN, acetonitrile (CH(3)CN), and formamide (HCONH(2)). Stable gaseous products of discharge chemistry were analyzed by selected ion flow tube mass spectrometry (SIFT-MS). Ratios of concentrations of the HNC/HCN isomers obtained using known transition dipole moments of rovibrational cold bands v(1) were found to be in the range 2.2-3%. A kinetic model was used to assess the roles the radical chemistry and ion chemistry play in the formation of these two isomers. Exclusion of the radical reactions from the model resulted in a value of the HNC/HCN ratio 2 orders of magnitude lower than the experimental results, thus confirming their dominant role. The major process responsible for the formation of the HNC isomer is the reaction of the HCN isomer with the H atoms. The rate constant determined using the kinetic model from the present data for this reaction is 1.13 (±0.2) × 10(-13) cm(3) s(-1).

Laser spark formamide decomposition studied by FT-IR spectroscopy.

High-resolution FT-IR spectroscopy was used for the analysis of the products of formamide dissociation using a high-energy Asterix laser. In the experiment, the detected products of the formamide LIDB dissociation were hydrogen cyanide, ammonia, carbon monoxide, carbon dioxide, nitrous oxide, hydroxylamine, and methanol. The molecular dynamics of the process was simulated with the use of a chemical model. The chemistry shared by formamide and the products of its dissociation is discussed with the respect to the formation of biomolecules.

A study of thermal decomposition and combustion products of disposable polyethylene terephthalate (PET) plastic using high resolution fourier transform infrared spectroscopy, selected ion flow tube mass spectrometry and gas chromatography mass spectrometry

The industrial production of poly (ethylene terephthalate), PET, continues to increase and thus it is important to understand the composition of fumes resulting from its disposal as a part of incinerated waste. In this study samples of PET material were combusted in a furnace corresponding to the German standard DIN 53,436 at temperatures of 500°C, 800°C (in an air flow) and also uncontrolled combustion in air. The gaseous products were then analysed using three different analytical methods: high resolution Fourier transform infrared spectroscopy (FTIR), selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry (GC-MS). Carbon dioxide, methane, ethylene, acetylene, formaldehyde (methanal) and acetaldehyde (ethanal) were detected by FTIR. Water, methane, acetaldehyde, ethylene, formaldehyde, methanol, acetone, benzene, terephthalic acid, styrene (ethenylbenzene), ethanol, toluene (methylbenzene), xylene (dimethylbenzene), ethylbenzene, naphthalene, biphenyl and phenol concentrations were all quantified by both SIFT-MS and GC-MS. Additionally, the fumes resulting from uncontrolled combustion in air were analysed by FTIR which resolves the rotation–vibration structure of the absorption bands of formaldehyde (2779.90 and 2778.48 cm−1) and propane, which was identified from characteristic vibrations of CH3 groups at 2977.00 and 2962.00 cm−1. The spectra were compared with reference standards.

Na I spectra in the 1.4–14 micron range: transitions and oscillator strengths involving f-, g-, and h-states

Context. Compared with the visible and ultraviolet ranges, fewer atomic and ionic lines are available in the infrared spectral region. Atlases of stellar spectra often provide only a short list of identified lines, and modern laboratory-based spectral features for wavelengths longer than 1 micron are not available for most elements. For the efficient use of the growing capabilities of infrared (IR) astronomy, detailed spectroscopical information on atomic line features in the IR region is needed. Aims. Parts of the infrared stellar (e.g., solar) spectra in the 1200–1800 cm −1 (5.6–8 μm) range have never been observed from the ground because of heavy contamination of the spectrum by telluric absorption lines. Such an infrared spectrum represents a great challenge for laboratory observations of new, unknown infrared atomic transitions involving the atomic levels with high orbital momentum and their comparison with the available spectra. Methods. The vapors of excited Na I atoms are produced during the ablation of the salt (sodium iodide, Na I) targets by a highrepetition rate (1.0 kHz) pulsed nanosecond ArF laser ExciStar S-Industrial V2.0 1000, pulse length 12 ns, λ = 193 nm, output energy of 15 mJ, fluence about 2–20 J/cm 2 inside a vacuum chamber (average pressure 10 −2 Torr). The time-resolved emission spectrum of the neutral atomic potassium (Na I) was recorded in the 700–7000 cm −1 region using the Fourier transform infrared spectroscopy technique with a resolution of 0.02 cm −1 .T hef -values calculated in the quantum-defect theory approximation are presented for the transitions involving the reported Na I levels. Results. This study reports precision laboratory measurements for 26 Na I lines in the range of 700–7000 cm −1 (14–1.4 μm), including 20 lines not measured previously in the laboratory. This results in newly observed 7h, 6h, and 6g levels, and improved energy determination for ten previously known levels. The doublet structure of the 4f level has been observed for the first time. For transitions between the observed levels, we report calculated f -values that agree reasonably well with experiment. Conclusions. The recorded Na I line features agree with the data from the available solar spectrum atlases. The energy values of Na I 4s, 4p, 5p, 6p, 4f, 5f, and 5g levels extracted from our spectra have lower uncertainties as compared to the values reported several decades ago, but the latter values slightly differ from ours.

Potassium spectra in the 700–7000 cm-1 domain: Transitions involving f-, g-, and h-states

Context. The infrared (IR) range is becoming increasingly important to astronomical studies of cool or dust-obscured objects, such as dwarfs, disks, or planets, and in the extended atmospheres of evolved stars. A general drawback of the IR spectral region is the much lower number of atomic lines available (relative to the visible and ultraviolet ranges). Aims. We attempt to obtain new laboratory spectra to help us identify spectral lines in the IR. This may result in the discovery of new excited atomic levels that are difficult to compute theoretically with high accuracy, hence can be determined solely from IR lines. Methods. The K vapor was formed through the ablation of the KI (potassium iodide) target by a high-repetition-rate (1.0 kHz) pulsed nanosecond ArF laser (λ = 193 nm, output energy of 15 mJ) in a vacuum (10 −2 Torr). The time-resolved emission spectrum of the neutral atomic potassium (K i) was recorded in the 700–7000 cm −1 region using the Fourier transform infrared spectroscopy technique with a resolution of 0.02 cm −1 .T hef -values calculated in the quantum-defect theory approximation are presented for the transitions involving the reported K i levels. Results. Precision laboratory measurements are presented for 38 K i lines in the infrared (including 25 lines not measured previously in the laboratory) range using time-resolved Fourier transform infrared spectroscopy. The 6g, 6h, and 7h levels of K i are observed for the first time, in addition to updated energy values of the other 23 K i levels and the f -values for the transitions involving these levels. Conclusions. The recorded wave numbers are in good agreement with the data from the available solar spectrum atlases. Nevertheless, we correct their identification for three lines (1343.699, 1548.559, and 1556.986 cm −1 ).

Formation of nucleobases in a Miller-Urey reducing atmosphere.

Significance The study shows that Miller–Urey experiments produce RNA nucleobases in discharges and laser-driven plasma impact simulations carried out in a simple prototype of reducing atmosphere containing ammonia and carbon monoxide. We carried out a self-standing description of chemistry relevant to hypothesis of abiotic synthesis of RNA nucleobases related to early-Earth chemical evolution under reducing conditions. The research addresses the chemistry of simple-model reducing atmosphere (NH3 + CO + H2O) and the role of formamide as an intermediate of nucleobase formation in Miller–Urey experiment. The explorations combine experiments performed using modern techniques of large, high-power shock wave plasma generation by hall terawatt lasers, electric discharges, and state-of-the-art ab initio free-energy calculations. The Miller–Urey experiments pioneered modern research on the molecular origins of life, but their actual relevance in this field was later questioned because the gas mixture used in their research is considered too reducing with respect to the most accepted hypotheses for the conditions on primordial Earth. In particular, the production of only amino acids has been taken as evidence of the limited relevance of the results. Here, we report an experimental work, combined with state-of-the-art computational methods, in which both electric discharge and laser-driven plasma impact simulations were carried out in a reducing atmosphere containing NH3 + CO. We show that RNA nucleobases are synthesized in these experiments, strongly supporting the possibility of the emergence of biologically relevant molecules in a reducing atmosphere. The reconstructed synthetic pathways indicate that small radicals and formamide play a crucial role, in agreement with a number of recent experimental and theoretical results.