Diagnostics of Nitrogen-methane Atmospheric Glow Discharge Used for a Mimic of Prebiotic Atmosphere

The exploration of planetary atmosphere is being advanced by the exciting results of the Cassin-Huygens mission to Titan. The complex chemistry revealed in such atmospheres leading to the synthesis of bigger molecules is providing new insights into our understanding of how life on Earth developed. This work extends our previous investigation of nitrogen-methane (N2-CH4) atmospheric glow discharge for simulation chemical processes in prebiotic atmospheres. In presented experiments 2 % of water vapor were addet to nitrogen-methane gas mixture. Exhaust products of discharge in this gas mixture were in-situ analysed by Fourier Transform Infra Red spectroscopy (FTIR). The major products identified in spectra were: hydrogen cyanide, acetylene and acetonitrile

Positive dc corona between coaxial electrodes in mixtures of carbon dioxide and oxygen

The positive corona discharge has been generated in a reactor equipped with a system of stainless steel cylindrical coaxial electrodes. The discharge has been fed with mixtures of carbon dioxide and oxygen (0–100% of oxygen) in flow-stopped regime. The time dependence of discharge current has been measured for a period of 1 h. The effect of the mixture composition on the discharge current and the onset voltage of the discharge has been investigated. A slight increase in the onset voltage was observed with increasing amount of oxygen in the gas mixture up to 20% of oxygen, where the maximum was reached. Then, with further increase of oxygen concentration, the onset voltage decreased. These results correspond to the measured discharge currents. The lowest currents were observed for a mixture containing 20% of oxygen, where the onset voltage is highest, and the highest currents were observed for pure oxygen, where the onset voltage is lowest. These observations are in agreement with Townsend's formula expressing the current–voltage characteristics of the discharge

Electron impact ionisation and UV absorption study of α- and β-pinene

We have performed a coordinated set of experiments to measure the electron impact ionisation and UV photoabsorption cross sections of α- and β-pinene. The adiabatic ionisation energies of α- and β-pinene were derived from experiment and found to be 8.3 and 8.6 eV which compared well with high-level quantum chemical calculations (G3MP2) yielding values of 8.29 and 8.41 eV. Additionally, vertical ionisation energies of 8.62 and 8.96 eV were calculated using an OVGF method. UV photoabsorption cross sections were measured using a high-resolution synchrotron radiation source and electronic states interpreted on the basis of the TD quantum chemical method

Experimental simulation of negative ion chemistry in Martian atmosphere using ion mobility spectrometry-mass spectrometry

We have studied the formation of negative ions in a negative Corona Discharge (CD) fed by CO2/N2 mixtures (with 0, 2, 4, 6, 8, 10% N2) using the technique of ion mobility spectrometry-orthogonal acceleration time of flight mass spectrometry (IMS-oaTOF). The composition of the negative ions was found to be dependent on the initial gas composition, the gas flow regime, the concentrations of neutral reactive species formed in the discharge and the trace amounts on water in the gases were found to play an important role in the negative ions formation. In a pure CO2 discharge operating under standard gas flow conditions of IMS (associated with strong interaction of ions with neutral reactive species formed in discharge) the ions CO3 - (H2O) and CO4 -(H2O) dominated the measured negative ion spectrum while in CO2/N2 mixtures NO3 -(H 2O) n, NO3 -(HNO3) (n = 0, 1) ions prevailed. In the case of reverse gas flow regime (low interaction of ions with neutral reactive species formed in discharge), the negative ions detected were O2 -(H2O) n, and O2 -.CO2(H2O) n both in pure CO2 and N2/CO2 mixtures. The spectra of negative ions recorded for a gas mixture containing 4% N2 in CO 2 were compared with theoretical predictions of negative ion composition in the lower atmosphere of Mars

Electron impact excitation of methane: determination of appearance energies for dissociation products

In this work, we present an experimental study of dissociative excitation of CH₄ utilizing a crossed electron molecular beam experiment. Methane was excited by nearly monochromatic electrons generated by a trochoidal electron monochromator. The dissociative products were identified on the basis of the emission spectra in the ultraviolet–visible (UV/VIS) spectral range. The excitation functions were recorded as the function of the electron energy for different emission bands of the fragments (Balmer series for H: n = 3,4...9→2, and moreover, CH: A²Δ→X²Π, CH: B²Σ⁻→ X²Π, CH: C²Σ⁺→ X²Π, CH⁺: B¹Δ→ A¹Π, and CI: 2p3s ¹Po₁→2p² ¹S₀). From the experimental data we have determined the threshold energies for excitation of particular fragments. Present experimental results indicate that the threshold energies for some dissociative excitation channels could be lower by ~1–2 eV in comparison to earlier studies and indicate that different dissociative processes may be operative at the threshold than assumed in the former studies