About

Igor Adamovich is a Professor of Mechanical and Aerospace Engineering at The Ohio State University, holding the John B. Nordholt Professorship in Mechanical Engineering or Materials Science and Engineering. His research interests center on the kinetics of nonequilibrium plasmas and high-speed nonequilibrium reacting flows, including molecular energy transfer, plasma-assisted combustion, plasma flow control, molecular lasers, laser diagnostics, and kinetic modeling. This research is conducted in the Non-Equilibrium Thermodynamics Laboratory (NETL).

Research topics

• Physics
• Chemistry
• Materials science
• Sociology
• Optics
• Mechanics
• Atomic physics
• Engineering
• Nanotechnology
• Nuclear physics
• Meteorology
• Optoelectronics
• Engineering physics
• Electrical engineering

Selected publications

• Control and In-Situ Diagnostics of N ₂ Vibrational Excitation With Hybrid AC-RF Plasma and Ferroelectric Electrode

  2026-01-08

  article

  Hybrid AC-RF discharges are a promising route for plasma-assisted ammonia synthesis, yet how hybrid waveforms redistribute energy into N2 vibrational modes and reshape discharge morphology remains poorly quantified. Here we study a hybrid AC-RF N2 ferroelectric barrier discharge driven by a 20 kHz AC voltage, with a sub-breakdown 13.56 MHz RF waveform applied between AC bursts and diagnose the plasma using synchronous ICCD imaging and time-resolved hybrid fs/ps N2 vibrational CARS over 13-40 torr. The ICCD images show that the hybrid AC-RF waveform broadens the discharge and distributes emission over a larger volume compared with AC-only operation, whereas RF alone remains strictly sub-breakdown with no visible emission. The N2 vibrational CARS spectra show that, over 13-40 torr, hybrid AC-RF plasmas populate vibrational levels up to v = 2 and yield N2 vibrational temperatures that are systematically higher than in the corresponding AC-only discharges, with the hybrid-induced enhancement in Tvib tending to increase with pressure and reaching up to ~1200 K at 40 torr. These results demonstrate that tailored AC-RF power coupling can efficiently channel energy into N2 vibrational modes, providing a tunable control on internal energy distributions for optimizing plasma-assisted ammonia synthesis and related electrified chemical processes.

  PublisherDOI

• Semiclassical Model of Nonadiabatic Energy Transfer in Atom-Molecule Collisions

  2026-01-08

  article1st authorCorresponding

  The recently developed semiclassical theory of nonadiabatic energy transfer in three-dimensional atom-atom collisions is extended to predict electronic excitation and quenching in atom-molecule collisions. The main assumption of the theory is the critical role of orbiting collisions, which result in multiple crossings of the seam between two potential energy surfaces during a single collision and enhance the net nonadiabatic transition probability. The projectile capture, which results in orbiting collisions, is modeled using the previously developed stochastic model of rotational energy transfer in atom-molecule collisions. The cross sections and rate coefficients predicted by the theory are compared with 3-D quasi-classical trajectory / surface hopping calculations and quantum scattering (wavepacket) calculations for N(2D)+N2↔N(4S)+N2, using the ab initio interaction potential energy surfaces and nonadiabatic coupling, and with the experimental data where available. Additional comparison with the quasi-classical trajectory / surface hopping calculations and experimental data is made for N(2D)+CO↔N(4S)+CO, demonstrating the range of applicability of the present approach. In both cases, the semiclassical theory predictions are in good agreement with the high-fidelity simulations at relatively low collision energies, up to 0.5-1.0 eV, and temperatures, up to T ~ 1000 K. At higher collision energies and temperatures, the theory appears to overpredict the energy transfer rate coefficients. This may be indicative of less efficient projectile capture and shorter lifetime of the atom-diatom transition complex. Approximate analytic expressions for the cross sections and rate coefficients are obtained. This approach may also be used to predict rate coefficients of electronic energy transfer in other atom-molecule collisions, for which the potential energy surfaces are available. The results provide the rate coefficients for the predictive simulations of low-temperature plasmas, and plasmas generated behind hypersonic shock waves.

  PublisherDOI

• Heated Supersonic Plasma Flow Reactor for Spectroscopic Measurements of Plasma Chemical Reaction Products

  2026-01-08

  articleSenior author

  A high-pressure heated plasma flow reactor excited by a ns pulse discharge, followed by a rapid supersonic expansion via a contoured nozzle, is used for time-resolved measurements of the products of plasma chemical reactions. The expansion is used to freeze the reactions and reduce the absorption linewidth, as well as the range of rotational states populated, to facilitate the detection of the reaction products by mid-IR laser absorption spectroscopy. The feasibility of this approach is demonstrated by the measurements of CO product in plasma-excited CO2-Ar and hydrocarbon-O2-Ar mixtures. In the experiment, a flow of the reactants passes through a thermal storage section, heated in a tube furnace. The heated flow is excited in a diffuse ns pulse discharge operated in burst mode. Downstream of the discharge excitation section, the flow expands through a contoured nozzle into a supersonic test section, with optical access provided via the side wall ports. Absorption in the test section is measured by a tunable quantum cascade mid-IR laser. The time-resolved flow temperature and the CO number density are inferred from the absorption line shape. The results are compared with the kinetic modeling predictions, quantifying the effect of the mixture composition, discharge burst duration, pulse repetition rate, and plenum temperature on the kinetics of plasma chemical reactions.

  PublisherDOI

• Measurements of Excited Metastable Atoms and Ground State Atoms in a Nonequilibrium Heated Plasma Flow Reactor

  2026-01-08

  articleSenior author

  Time-resolved, absolute populations of metastable atoms, N(2D,2P), and ground state atoms, N(4S) and O(3P), are measured in nitrogen and in a 1000 ppm NO-N2 mixture diluted in Ar, in a heated plasma flow reactor, at T=300-800 K. The flow in the reactor is excited by the ns pulse discharge bursts operated at a high pulse repetition rate, 100 kHz, generating a diffuse plasma with well-defined boundaries. The atomic species in the main ns pulse discharge are measured by the Atomic Resonance Absorption Spectroscopy (ARAS), using the vacuum UV emission produced by a probe discharge, operating at the same conditions. The results are corrected for the self-absorption of the incident resonance radiation in the probe discharge, before it is absorbed in the main discharge. No metastable O(1D) or O(1S) atoms have been detected. The focus of the future work is the verification of the ARAS data using the broadband VUV absorption spectroscopy, calibrated in inert gas mixtures (Xe and Kr), and measurements of NO+ ions, by mid-IR Cavity Ring Down Spectroscopy, to infer the rates of associative ionization in collisions of excited metastable atoms in the afterglow.

  PublisherDOI

• O Atom Generation and Decay in O ₂ -Ar Mixtures Dissociated by a Ns Pulse Discharge in a Heated Plasma Flow Reactor

  2026-01-08

  articleSenior author

  Kinetics of O atom generation and decay is studied in O2-Ar mixtures in a heated plasma flow reactor with optical access for laser diagnostics. The O atom number density is measured by fs Two-Photon Absorption Laser Induced Fluorescence (TALIF), calibrated in xenon. In addition, an alternative calibration approach is used, where most of O2 molecules in the reactant mixture (0.125% O2-Ar) dissociate into O atoms, due to the rapid energy transfer from excited Ar atoms, such that their number density approaches twice the original O2 number density. The present method is not affected by the uncertainty in the O / Xe two-photon absorption cross section ratio and can be used to assess the applicability of O TALIF calibration in Xe for fs TALIF. Time resolved, absolute O atom number densities are measured in preheated O2-Ar mixtures partially dissociated by a burst of ns discharge pulses (up to 300 pulses/burst at 80 kHz) and in the afterglow. The measurements are made at the furnace temperature of T=400 K, P=200 Torr, and O2 mole fractions ranging from 0.125% to 20%. The O atom number densities in mixtures with O2 mole fractions higher than 0.125% are obtained by scaling the respective fluorescence yields.

  PublisherDOI

• Semiclassical analytic theory of multi-channel electronic energy transfer in nonadiabatic atomic collisions

  The Journal of Chemical Physics · 2025-12-10

  article1st authorCorresponding

  The semiclassical theory of nonadiabatic energy transfer [Adamovich and Rich, J. Chem. Phys. 160, 194101 (2024)] is extended to include multi-channel electronic excitation and quenching in three-dimensional atomic collisions. The transition probabilities, cross sections, and rate coefficients predicted by the theory are compared with high-fidelity quantum scattering predictions for N + N, using state-of-the-art ab initio interaction potentials and nonadiabatic couplings, and with a few available experiments. The theory predictions are in good agreement with quantum scattering, both for conditions where the energy transfer is dominated by a single pair of adiabatic potentials and in cases where the energy transfer is affected by additional intermediate states. These cases include multiple curve crossings encountered during a single collision and pathways with the formation of closed channels, resulting in multiple resonances. The latter case is of particular interest, since it cannot be reduced to the interaction of individual potential pairs. Analytic expressions for the cross sections and rate coefficients are obtained using the same approach as in our previous work. The results quantify the effect of multi-channel interactions on the dynamics of energy transfer in atomic collisions. This approach can also be used to predict rate coefficients for electronic energy transfer in N + O and O + O collisions, as well as other atomic species collisions, such as involving Ar or He, over a wide range of temperatures. The fidelity of the theory predictions depends on the availability of accurate potentials for the interacting excited electronic states and their coupling (both spin-orbit and derivative). The results provide rate coefficients for the predictive simulation of low-temperature plasmas and plasmas generated behind hypersonic shock waves.

  PublisherDOI

• Three-temperature collisional-radiative model of ionization and recombination in hypersonic air plasmas

  Physics of Plasmas · 2025-10-01 · 3 citations

  articleOpen accessSenior author

  A three-temperature electronic state-resolved kinetic model is developed to study nonequilibrium ionization and electron recombination in shock-heated and expanding hypersonic air-argon plasmas. Leveraging a recently published semiclassical analytic theory, a novel set of rate coefficients for heavy particle impact electronic excitation in atomic collisions involving N and O are determined and incorporated into the model. The state-resolved kinetics are then coupled with the one-dimensional steady Euler equations to study ionizing flows behind 3–14 km/s shock waves and recombining flows in supersonic nozzles. Electron number density predictions are evaluated using experimental data for both of these flow configurations. Next, leveraging the high-quality rate data for electronic excitation, relaxation times characterizing translational to electronic energy exchange are computed for 41 collider pairs. In most cases, the relaxation times are slower than comparable vibrational relaxation times; however, for N2–N and O2–O, electronic excitation and vibrational relaxation proceed on similar timescales, indicating that molecular excited states may become populated during, and contribute to, dissociation. The impact of nonequilibrium atomic metastable state populations on the net rate of associative ionization is then assessed. When electronic nonequilibrium effects are neglected, the ionization distance is underpredicted by up to 50% at 9 km/s. Such errors can be mitigated by adopting Ttr0.5Tvib0.5 as the rate controlling temperature for associative ionization. Finally, the nonequilibrium behavior of electron impact ionization is studied in detail. Results support the validity of the quasi-steady-state (QSS) assumption for ionizing air mixtures behind strong shock waves.

  PublisherDOI

• Plasma-catalytic ammonia generation and plasma-chemical nitrogen oxidation in a ‘hybrid’ ns pulse/RF discharge

  Plasma Sources Science and Technology · 2025-05-23 · 4 citations

  articleOpen accessSenior author

  Abstract Plasma-catalytic ammonia synthesis in a ‘hybrid’ ns pulse/RF discharge, operated in the repetitive burst mode, is studied by Fourier transform infrared absorption spectroscopy. The data are taken in preheated H 2 -N 2 mixtures, with and without Ni/ γ -Al 2 O 3 , Rh/ γ -Al 2 O 3 , and Ru/ γ -Al 2 O 3 catalyst placed in the plasma flow reactor. The sub-breakdown RF waveform added to the ns pulse bursts is used to isolate the effect of the enhanced vibrational excitation of N 2 on ammonia and nitric oxide yields. The enhancement of the N 2 vibrational temperature in the hybrid N 2 –H 2 plasma has been demonstrated in our previous work. Adding the RF waveform results in a reproducible increase of the ammonia yield, measured over the ‘blank’ alumna, Ni, Rh, and Ru catalyst samples, by up to 25% compared to the ns pulse discharge operating alone. The yield enhancement in the empty reactor (without the alumina or catalyst samples) is significantly lower, about 10%. This indicates that the surface exposed to the plasma is an essential factor for the RF enhancement. The effect scales with the number of RF-augmented pulses per burst. In a closely related experiment, nitric oxide yield in preheated O 2 –N 2 mixtures excited by the hybrid ns/RF discharge in the empty reactor was compared to that in a ns pulse discharge operating alone, at the same conditions. Significant enhancement of NO yield in the hybrid discharge has been detected, up to 50%. Measurements of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mrow> <mml:msup> <mml:mi>A</mml:mi> <mml:mn>3</mml:mn> </mml:msup> </mml:mrow> <mml:msubsup> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">Σ</mml:mi> </mml:mrow> </mml:mrow> <mml:mi>u</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> populations in ns/RF and ns pulse discharges did not show evidence of additional generation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>A</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> , N, H, or O atoms by the sub-breakdown RF waveform. We conclude that the NH 3 yield enhancement is likely caused by the surface reactions of vibrationally excited nitrogen, leading to its dissociation on the surface, while the NO yield is enhanced by the reactions of vibrationally excited nitrogen in the plasma volume.

  PublisherDOI

• Semiclassical Analytic Theory of Multi-Channel Electronic Energy Transfer in Nonadiabatic Atomic Collisions

  2025-01-03 · 1 citations

  article1st authorCorresponding

  A previously developed semiclassical theory of nonadiabatic energy transfer is extended to analyze multi-channel electronic excitation and quenching in three-dimensional atomic collisions. The predicted transition probabilities, cross sections, and rate coefficients are compared with the quantum scattering calculations for N + N, using the ab initio interaction potentials and nonadiabatic coupling, and with the experimental data where available. The theory predictions are in good agreement with quantum scattering, both at the conditions where the energy transfer is dominated by a single pair of adiabatic potentials and in cases where the energy transfer is affected by additional intermediate states, specifically involving the pathways with the formation of closed channels resulting in multiple resonances. The latter case is of particular interest, since it cannot be reduced to the interaction of individual potential pairs. Analytic expressions for the cross sections and rate coefficients are obtained using the same approach as in our previous work. The results quantify and illustrate the effect of the multi-channel interaction on the dynamics of the energy transfer. The same approach can be used to predict the rate coefficients of electronic excitation and quenching in collisions of N + O and O + O, as well as other atomic species over a wide range of temperatures. The fidelity of these predictions depends on the availability of the accurate potentials for the interacting excited electronic states and their coupling (both spin-orbit and derivative). The results provide the rate coefficients for the predictive simulations of plasma flows behind hypersonic shock waves.

  PublisherDOI

• Measurements of Excited Metastable Atoms in a Nonequilibrium Heated Plasma Reactor

  2025-01-03

  articleSenior author

  Metastable nitrogen atoms, N(2D) and N(2P), generated in a ns pulse discharge burst in nitrogen in a plasma flow reactor have been measured by Atomic Resonance Absorption Spectroscopy (ARAS), using the vacuum UV emission produced by a “probe” ns pulse discharge near 149 nm and 174 nm. Time-resolved, absolute N(2D,2P) number densities are inferred from the absorption measurements. ARAS may also be employed for the measurements of the ground state O(3P) atoms in N2-NO mixtures, using the O atoms line near 130 nm. The broadband vacuum UV absorption measurements using a deuterium lamp as a light source did not result in detectable absorption by N(2D) and N(2P). This is due to the relatively low spectrometer resolution and significant photomultiplier tube (PMT) detector noise when measuring a continuous wave signal from the lamp. Future broadband absorption measurements will use a gated VUV-sensitive camera as a detector. The measurement results will be compared with kinetic modeling, and used to predict the rates of associative ionization in nonequilibrium nitrogen and air.

  PublisherDOI

Recent grants

• Nanosecond Pulse Discharges at a Liquid-Vapor Interface and in Liquids: Discharge Dynamics and Plasma Chemistry

  NSF · $384k · 2016–2020

• Fundamental Studies of Accelerated Low Temperature Combustion Kinetics by Nonequilibrium Plasmas

  NSF · $300k · 2014–2017

Frequent coauthors

• Walter Lempert

  The Ohio State University

  138 shared

• J. William Rich

  The Ohio State University

  101 shared

• Peter Palm

  The Ohio State University

  67 shared

• Munetake Nishihara

  Plasma (Russia)

  65 shared

• John Martin Rich

  59 shared

• Kraig Frederickson

  The Ohio State University

  51 shared

• Elijah Jans

  49 shared

• W. Lempert

  38 shared