Dr Antonin Knizek

Abstract:

<p>Benzene is the simplest organic compound with a 6-carbon aromatic ring. As such, it was used as a first order representative of aromatic compounds in planetary atmospheres. These compounds can be brought by asteroid impacts into rocky planetary atmospheres, where they can serve as precursors for further synthesis. Our experiments show that benzene vapours in nitrogen-dominated atmospheres subjected to asteroid impacts (modelled by laboratory laser shots) lead to the formation of acetylene and hydrogen cyanide. Both these products appear in many proposed mechanisms of prebiotic chemistry.</p>

Abstract:

AbstractThe high‐energy‐density synthesis of NxOy species is simulated in gas mixtures representing an O2‐free early‐Earth atmosphere by terawatt‐kilojoule‐class laser‐induced dielectric breakdown (LIDB). These experiments differ from previous LIDB experiments due to the 100 times greater energy delivered per pulse and sensitive analysis of products by high‐resolution infrared spectroscopy. The measured yields of NO, N2O, and NO2 are 0.08–8 × 1015, 5 × 1012, and 0.03–7 × 1014 molec J −1. The high N2O yield is above the upper‐limit constraint of previous tabletop LIDB experiments and the expected yield of a thermochemical freeze‐out at any temperature between 2000 and 5000 K, while the NO and NO2 yields are in broad agreement with freeze‐out models. Using a one dimensional chemical model of the Hadean atmosphere and a simple model of late bombardment, we compute the source flux of N2O assuming the same high production yield as measured experimentally and find the steady‐state partial pressure of N2O is insufficient to warm the climate.

Abstract:

Examination of thermal decomposition of street samples of cocaine and methamphetamine shows that typical products detected in previous studies are accompanied by a wide palette of simple volatile compounds easily detectable by spectral techniques. These molecules increase smoke toxicity and their spectral detection can be potentially used for identification of drug samples by well-controlled laboratory thermolysis in temperature progression. In our study, street samples of cocaine and methamphetamine have been thermolyzed under vacuum over the temperature range of 350-650 °C. The volatile products (CO, HCN, CH₄, C₂H₄, etc.) have been monitored by high-resolution Fourier-transform infrared (FTIR) spectrometry in this temperature range. The decomposition mechanism has been additionally examined theoretically by quantum-chemical calculations for the highest temperature achieved experimentally in our study and beyond. Prior to analysis, the street samples have also been characterized by FTIR, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and melting point determination.