Joshua H. Baraban’s research while affiliated with Ben-Gurion University of the Negev and other places

We utilized a combination of experimental alongside data-driven and theoretical modelling techniques to study non-thermal plasma properties and observables including optical emission spectral intensities, electron temperature, species concentrations, degree of ionization, and reaction rates. As a case study we measured the plasma properties of Argon gas in the low-pressure regime using optical emission spectroscopy (OES) while varying plasma input power and gas flow rate. We used data-driven and drift-diffusion modeling techniques to obtain complementary information, including electron temperature, reduced electric field, and species densities. The calculated density number of excited argon has a linear correlation to measured emission intensity, and we found that the dominant effect on Ar I intensity is the applied power with the gas flow (or pressure) the secondary factor (77% and 20%, respectively). The electron temperature increases with power but decreases with flow (or pressure). Combining the measured and modelling results help to understand the cold plasma dynamics and chemistry towards more complex plasma chemistry applications.

We report a rotationally resolved spectroscopic detection scheme for vibrationally excited molecular oxygen with high sensitivity. Two-color (2 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of O2 hot bands were recorded for the first time via the 3dπ(v′=0)←X3Σg− (v″ = 1) Rydberg transitions. Spectroscopic constants and relative Franck–Condon factors were extracted and compared to simulations. This new access to quantum-state-resolved diagnostics of vibrationally excited O2 promises to shed light on the physical and chemical dynamics of many processes.

A shared ambition of molecular spectroscopy and molecular dynamics is to establish the truths of chemical intuition on solid physical bedrock. Experimental characterization of the transition state was thought unattainable, but modern techniques have begun to achieve the incredible.

We utilized a combination of experimental alongside data-driven and theoretical modelling techniques to study non-thermal plasma properties and observables including optical emission spectral intensities, electron temperature, species concentrations, degree of ionization, and reaction rates. As a case study we measured the plasma properties of Argon gas in the low-pressure regime using optical emission spectroscopy (OES) while varying plasma input power and gas flow rate. We used data-driven and drift-diffusion modeling techniques to obtain complementary information, including electron temperature, reduced electric field, and species densities. The calculated density number of excited argon has a linear correlation to measured emission intensity, and we found that the dominant effect on Ar I intensity is the applied power with the gas flow (or pressure) the secondary factor (77% and 20%, respectively). The electron temperature increases with power but decreases with flow (or pressure). Combining the measured and modelling results help to understand the cold plasma dynamics and chemistry towards more complex plasma chemistry applications.

The behavior of mixed composition cold non-equilibrium plasmas was investigated in a low-pressure capacitively coupled reactor using optical emission spectroscopy (OES). By fitting experimental data to simulations of the Second Positive System (C3 Πu-B3Πg) of N2, rotational and vibrational temperatures were determined for various Ar/N2 mixtures as a function of plasma input power (40-100 W) and pressure (300-700 mTorr). Simulations of the plasma were performed for comparison. For pure N2, the observed trends revealed that both the rotational and vibrational temperatures increased with input power, (Trot of v=0 increased from 369-396 K and Tvib from 5938-6542 K, at 40-100 W, 100 SCCM and 293 mTorr) but both temperatures showed minimal response to the applied changes in pressure. The rotational and vibrational temperatures for the mixed composition Ar/N2 plasmas were significantly higher compared to the pure N2 plasmas (e.g. Trot of 1308 K and Tvib of 7279 K for 1.8% of N2 in Ar; at 50 W, 4 SCCM of N2, 220 SCCM of Ar for a total pressure of 587 mTorr). Moreover, the addition of Ar caused a larger separation between the rotational and vibrational temperatures compared to the pure N2 case. These phenomena illustrate the effects of Ar on the non-equilibrium energy distribution and more generally the influence that the gas mixture composition may have on the plasma reactivity.

Despite their prevalence in biomass and importance in biochemistry, there is still much to be learned about simple carbohydrates. Gas-phase calculations are reported here on two trioses and three tetroses. For aldotetroses, both the open-chain and furanose forms are considered. Enthalpies of reduction to polyols are calculated at the CBS-APNO level of theory, and comparisons to simple aldehydes and ketones are made. Heats of formation are calculated in two ways with overall good agreement. The heat of formation of glyceraldehyde obtained from modified HEAT calculations is also reported. Finally, calculated bond energies are presented, and the influence of the structure on the bond energies is discussed.