Ilia Dubinsky - Academia.edu (original) (raw)
Papers by Ilia Dubinsky
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.Includes bibliog... more Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.Includes bibliographical references.by Ilia A. Dubinsky.Ph.D
The Journal of Physical Chemistry, 1995
The kinetics of the reaction CH3CHC1+ 0 2 F?. CH3CHC102products (1) has been studied at temperatu... more The kinetics of the reaction CH3CHC1+ 0 2 F?. CH3CHC102products (1) has been studied at temperatures 296-839 K and He densities of (3-49) x 10l6 molecule cm-3 by laser photolysis/photoionization mass spectrometry. Rate constants were determined in time-resolved experiments as a function of temperature and bath gas density. At low temperatures (298-400 K) the rate constants are in the falloff region under the conditions of the experiments. Relaxation to equilibrium in the addition step of the reaction was monitored within the temperature range 520-590 K. Equilibrium constants were determined as a function of temperature and used to obtain the enthalpy and entropy of the addition step of the reaction (1). At high temperatures (750-839 K) the reaction rate constant is independent of both pressure and temperature within the uncertainty of the experimental data and equal to (1.2 f 0.4) x cm3 molecule-' s-'. Vinyl chloride (C2H3C1) was detected as a major product of reaction 1 at T = 800 K. The rate constant of the reaction CH3CHC1 + C12 products (6) was determined at room temperature and He densities of (9-36) x 10l6 molecule cm-3 using the same technique. The value obtained is k6 = (4.37 f 0.69) x cm3 molecule-' s-'. An estimate of the high-pressure limit for reaction 1 was determined using this measured k6 and the kl/k6 ratio obtained by Kaiser et al.:l k"1 (T=298K) = (1.04 f 0.22) x lo-" cm3 molecule-' s-'. In a theoretical part of the study, structure, vibrational frequencies, and energies of nine conformations of CH3CHC102 were calculated using ab initio UHF/6-31G* and MP2/6-31G** methods. The theoretical results are used to calculate the entropy change of the addition reaction As0298 =-152.3 f 3.3 J mol-' K-'. Th~s entropy change combined with the experimentally determined equilibrium constants resulted in a CH3CHC1-02 bond energy m 2 9 8 =-131.2 f 1.8 kJ mol-l. The rooq-temperature entropy (S O 2 9 8 = 341.0 f 3.3 J mol-' K-') and the heat of formation (A H f o~9 8 =-54.7 f 3.7 kJ mol-') of the CH3CHC102 adduct were obtained.
The Journal of Physical Chemistry, 1994
Experimental and Theoretical Study of the sec-C4H9 CH3 + C3H6 Reaction ... Vadim D. Knyazev,'... more Experimental and Theoretical Study of the sec-C4H9 CH3 + C3H6 Reaction ... Vadim D. Knyazev,' Ilia A. Dubinsky$ Irene R. Slagle, and David Gutmans Department of Chemistry, Catholic University of America, Washington, DC 20064 Received: May 20, 1994; In Final Form: ...
Symposium (International) on Combustion, 1994
The kinetics of the unimolecular decomposition of the 1-chloroethyl radical have been studied. Th... more The kinetics of the unimolecular decomposition of the 1-chloroethyl radical have been studied. The reaction was isolated for quantitative study in a heated tubular flow reactor coupled to a photoionization mass spectrometer. Rate constants for the decomposition were obtained in time-resolved experiments as a function of temperature (848--980 K) and bath gas density (3--22 {times} 10{sup 16} molecule/cm{sup 3}) in He, Ar, and N{sub 2}. The rate constants are in the falloff under the conditions of the experiments. The falloff behavior was analyzed using a Master Equation analysis. A transition state model was created to obtain values of the microcanonical rate constants, k(E), needed to solve the Master Equation. The transition state model provides the high-pressure limit rate constants for the decomposition reaction (k{sub 1}{sup {infinity}} (CH{sub 3}CHCl = CH{sub 2}CHCl + H) = 1.94 {times} 10{sup 9} T{sup 1.22} exp({minus}19,510 K/T)/s) and the reverse reaction (k{sub {minus}1}{sup {infinity}} (H + CH{sub 2}CHCl = CH{sub 3}CHCl + H) = 3.35 {times} 10{sup {minus}14} T{sup 0.86} exp({minus}75.3 K/T) cm{sup 3}/molecule s). Values of {l_angle}{Delta}E{r_angle}{sub down} for the energy loss probability were obtained for each experiment using the exponential-down model. The values of {l_angle}{Delta}E{r_angle}{sub down} display a pronounced positive temperature dependence withmore » average values of 255 (He), 360 (Ar), and 261 (N{sub 2}) cm{sup {minus}1}. Parameterization of the temperature and pressure dependence of the unimolecular rate constant for the temperature range 298--1,500 K and pressures 0.001--10 atmospheres is provided using the modified Lindemann-Hinshelwood expression.« less
The Journal of Physical Chemistry, 1994
The unimolecular decomposition of the alkyl radicals is an integral part of all high-temperature ... more The unimolecular decomposition of the alkyl radicals is an integral part of all high-temperature hydrocarbon pyrolysis and oxidation mechani~ms.l-~ Knowledge of kinetics of these reactions is essential for accurate modeling of the physical and chemical behavior of flames and ...
In a cavity ring-down experiment with pulsed lasers it is usually difficult to obtain purely expo... more In a cavity ring-down experiment with pulsed lasers it is usually difficult to obtain purely exponential ring-down signals due to transverse mode beats. The mode beat patterns usually change randomly from pulse to pulse as a result of the transverse energy ...
In a pulsed ring-down experiment, where the mirror reflectivity is high and consequently the ring... more In a pulsed ring-down experiment, where the mirror reflectivity is high and consequently the ring-down time is long (approx10times10−0s)(\ approx 10\ times 10^{-0} s) (approx10times10−0s) the time constant of the photo-detector is usually chosen to be long enough, such that ripples due to the round trips in ...
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.Includes bibliog... more Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1998.Includes bibliographical references.by Ilia A. Dubinsky.Ph.D
The Journal of Physical Chemistry, 1995
The kinetics of the reaction CH3CHC1+ 0 2 F?. CH3CHC102products (1) has been studied at temperatu... more The kinetics of the reaction CH3CHC1+ 0 2 F?. CH3CHC102products (1) has been studied at temperatures 296-839 K and He densities of (3-49) x 10l6 molecule cm-3 by laser photolysis/photoionization mass spectrometry. Rate constants were determined in time-resolved experiments as a function of temperature and bath gas density. At low temperatures (298-400 K) the rate constants are in the falloff region under the conditions of the experiments. Relaxation to equilibrium in the addition step of the reaction was monitored within the temperature range 520-590 K. Equilibrium constants were determined as a function of temperature and used to obtain the enthalpy and entropy of the addition step of the reaction (1). At high temperatures (750-839 K) the reaction rate constant is independent of both pressure and temperature within the uncertainty of the experimental data and equal to (1.2 f 0.4) x cm3 molecule-' s-'. Vinyl chloride (C2H3C1) was detected as a major product of reaction 1 at T = 800 K. The rate constant of the reaction CH3CHC1 + C12 products (6) was determined at room temperature and He densities of (9-36) x 10l6 molecule cm-3 using the same technique. The value obtained is k6 = (4.37 f 0.69) x cm3 molecule-' s-'. An estimate of the high-pressure limit for reaction 1 was determined using this measured k6 and the kl/k6 ratio obtained by Kaiser et al.:l k"1 (T=298K) = (1.04 f 0.22) x lo-" cm3 molecule-' s-'. In a theoretical part of the study, structure, vibrational frequencies, and energies of nine conformations of CH3CHC102 were calculated using ab initio UHF/6-31G* and MP2/6-31G** methods. The theoretical results are used to calculate the entropy change of the addition reaction As0298 =-152.3 f 3.3 J mol-' K-'. Th~s entropy change combined with the experimentally determined equilibrium constants resulted in a CH3CHC1-02 bond energy m 2 9 8 =-131.2 f 1.8 kJ mol-l. The rooq-temperature entropy (S O 2 9 8 = 341.0 f 3.3 J mol-' K-') and the heat of formation (A H f o~9 8 =-54.7 f 3.7 kJ mol-') of the CH3CHC102 adduct were obtained.
The Journal of Physical Chemistry, 1994
Experimental and Theoretical Study of the sec-C4H9 CH3 + C3H6 Reaction ... Vadim D. Knyazev,'... more Experimental and Theoretical Study of the sec-C4H9 CH3 + C3H6 Reaction ... Vadim D. Knyazev,' Ilia A. Dubinsky$ Irene R. Slagle, and David Gutmans Department of Chemistry, Catholic University of America, Washington, DC 20064 Received: May 20, 1994; In Final Form: ...
Symposium (International) on Combustion, 1994
The kinetics of the unimolecular decomposition of the 1-chloroethyl radical have been studied. Th... more The kinetics of the unimolecular decomposition of the 1-chloroethyl radical have been studied. The reaction was isolated for quantitative study in a heated tubular flow reactor coupled to a photoionization mass spectrometer. Rate constants for the decomposition were obtained in time-resolved experiments as a function of temperature (848--980 K) and bath gas density (3--22 {times} 10{sup 16} molecule/cm{sup 3}) in He, Ar, and N{sub 2}. The rate constants are in the falloff under the conditions of the experiments. The falloff behavior was analyzed using a Master Equation analysis. A transition state model was created to obtain values of the microcanonical rate constants, k(E), needed to solve the Master Equation. The transition state model provides the high-pressure limit rate constants for the decomposition reaction (k{sub 1}{sup {infinity}} (CH{sub 3}CHCl = CH{sub 2}CHCl + H) = 1.94 {times} 10{sup 9} T{sup 1.22} exp({minus}19,510 K/T)/s) and the reverse reaction (k{sub {minus}1}{sup {infinity}} (H + CH{sub 2}CHCl = CH{sub 3}CHCl + H) = 3.35 {times} 10{sup {minus}14} T{sup 0.86} exp({minus}75.3 K/T) cm{sup 3}/molecule s). Values of {l_angle}{Delta}E{r_angle}{sub down} for the energy loss probability were obtained for each experiment using the exponential-down model. The values of {l_angle}{Delta}E{r_angle}{sub down} display a pronounced positive temperature dependence withmore » average values of 255 (He), 360 (Ar), and 261 (N{sub 2}) cm{sup {minus}1}. Parameterization of the temperature and pressure dependence of the unimolecular rate constant for the temperature range 298--1,500 K and pressures 0.001--10 atmospheres is provided using the modified Lindemann-Hinshelwood expression.« less
The Journal of Physical Chemistry, 1994
The unimolecular decomposition of the alkyl radicals is an integral part of all high-temperature ... more The unimolecular decomposition of the alkyl radicals is an integral part of all high-temperature hydrocarbon pyrolysis and oxidation mechani~ms.l-~ Knowledge of kinetics of these reactions is essential for accurate modeling of the physical and chemical behavior of flames and ...
In a cavity ring-down experiment with pulsed lasers it is usually difficult to obtain purely expo... more In a cavity ring-down experiment with pulsed lasers it is usually difficult to obtain purely exponential ring-down signals due to transverse mode beats. The mode beat patterns usually change randomly from pulse to pulse as a result of the transverse energy ...
In a pulsed ring-down experiment, where the mirror reflectivity is high and consequently the ring... more In a pulsed ring-down experiment, where the mirror reflectivity is high and consequently the ring-down time is long (approx10times10−0s)(\ approx 10\ times 10^{-0} s) (approx10times10−0s) the time constant of the photo-detector is usually chosen to be long enough, such that ripples due to the round trips in ...