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M. B. Trzhaskovskaya - One of the best experts on this subject based on the ideXlab platform.
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Internal Conversion Coefficients - How good are they now?
ND2007, 2007Co-Authors: Tibor Kibedi, M. B. Trzhaskovskaya, T.w. Burrows, C.w. Nestor, Paul DavidsonAbstract:Internal Conversion coefficients involving atomic electrons (ICC) and electron-positron pairs (IPC) are often required to determine transition multipolarities and total transition rates. A new Internal Conversion coefficient data base, BrIcc has been developed which integrates a number of tabulations on ICC and IPC, as well as {Omega}(E0) electronic factors. To decide which theoretical Internal Conversion coefficient table to use, the accurately determined experimental {alpha}{sub K}, {alpha}{sub L}, {alpha}{sub Total} and {alpha}{sub K}/{alpha}{sub L} values were compared with the new Dirac-Fock calculations using extreme assumptions on the effect of the atomic vacancy. While the overall difference between experiment and theory is less than 1%, our analysis shows preference towards the so called ''Frozen Orbital'' approximation, which takes into account the effect of the atomic vacancy.
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Internal Conversion in hydrogen-like ions
Physics of Atomic Nuclei, 2004Co-Authors: F. F. Karpeshin, Yu. N. Novikov, M. B. TrzhaskovskayaAbstract:The probability of Internal gamma-ray Conversion is theoretically investigated for hydrogen-like ions versus the corresponding neutral atoms. The relevant calculations are performed by the relativistic Dirac-Fock method. The results reveal that the effect of multiple ionization on the coefficients of Internal Conversion in the K shell is maximal near the ionization threshold and for transitions of high multipole order, where this effect can be as great as a few orders of magnitude. The distinction between the coefficient of Internal Conversion in the K shell of a neutral atom and that in the respective hydrogen-like ion decreases with increasing transition energy, but it remains sizable for transitions of practical importance. It is found that the ionization of an atom to a hydrogen-like ion with allowance for Conversion in external atomic shells may change significantly (by up to eight orders of magnitude) the lifetime of the nucleus being considered. The predicted effects can be observed in experiments with beams of relativistic heavy ions.
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Internal Conversion to bound final states in Te
Nuclear Physics A, 2000Co-Authors: M. R. Harston, F. F. Karpeshin, J. F. Chemin, T. Carreyre, M. B. TrzhaskovskayaAbstract:Abstract Theoretical results are presented for rate of decay of the 3/2+ isomeric nuclear state of 125 Te by excitation of atomic electrons to bound states in the ions Te 45+ and Te 46+ . In these ions the nuclear transition energy lies just below the threshold for emission of a K-shell electron to the continuum with the result that normal K-shell Internal Conversion is energetically forbidden. However recent experimental results indicate that excitation of K-shell electrons is still significant in these ions. The theoretical results presented here for Internal Conversion to bound final states are in quantitative agreement with experiment and thereby confirm the contribution of near-resonant electron–nucleus transitions involving a bound final state.
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Subthreshold Internal Conversion to bound states in highly ionized 125Te ions.
Physical review. C Nuclear physics, 1996Co-Authors: F. F. Karpeshin, M. R. Harston, F. Attallah, J. F. Chemin, J. N. Scheurer, I. M. Band, M. B. TrzhaskovskayaAbstract:A new mode of Internal Conversion decay, in which the converted electron is excited to a bound orbital instead of a continuum orbital, is discussed. General theoretical results are presented for the relation between bound Internal Conversion and continuum Internal Conversion of the nucleus. It is shown that the transition rate for Internal Conversion decay is continuous across the energy threshold between continuum final states and bound final states. Theoretical predictions for decay to bound states of $^{125}\mathrm{Te}$ are consistent with experimental data on Internal Conversion in highly charged ions of this nuclide. \textcopyright{} 1996 The American Physical Society.
F. F. Karpeshin - One of the best experts on this subject based on the ideXlab platform.
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Internal Conversion in hydrogen-like ions
Physics of Atomic Nuclei, 2004Co-Authors: F. F. Karpeshin, Yu. N. Novikov, M. B. TrzhaskovskayaAbstract:The probability of Internal gamma-ray Conversion is theoretically investigated for hydrogen-like ions versus the corresponding neutral atoms. The relevant calculations are performed by the relativistic Dirac-Fock method. The results reveal that the effect of multiple ionization on the coefficients of Internal Conversion in the K shell is maximal near the ionization threshold and for transitions of high multipole order, where this effect can be as great as a few orders of magnitude. The distinction between the coefficient of Internal Conversion in the K shell of a neutral atom and that in the respective hydrogen-like ion decreases with increasing transition energy, but it remains sizable for transitions of practical importance. It is found that the ionization of an atom to a hydrogen-like ion with allowance for Conversion in external atomic shells may change significantly (by up to eight orders of magnitude) the lifetime of the nucleus being considered. The predicted effects can be observed in experiments with beams of relativistic heavy ions.
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Internal Conversion to bound final states in Te
Nuclear Physics A, 2000Co-Authors: M. R. Harston, F. F. Karpeshin, J. F. Chemin, T. Carreyre, M. B. TrzhaskovskayaAbstract:Abstract Theoretical results are presented for rate of decay of the 3/2+ isomeric nuclear state of 125 Te by excitation of atomic electrons to bound states in the ions Te 45+ and Te 46+ . In these ions the nuclear transition energy lies just below the threshold for emission of a K-shell electron to the continuum with the result that normal K-shell Internal Conversion is energetically forbidden. However recent experimental results indicate that excitation of K-shell electrons is still significant in these ions. The theoretical results presented here for Internal Conversion to bound final states are in quantitative agreement with experiment and thereby confirm the contribution of near-resonant electron–nucleus transitions involving a bound final state.
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Subthreshold Internal Conversion to bound states in highly ionized 125Te ions.
Physical review. C Nuclear physics, 1996Co-Authors: F. F. Karpeshin, M. R. Harston, F. Attallah, J. F. Chemin, J. N. Scheurer, I. M. Band, M. B. TrzhaskovskayaAbstract:A new mode of Internal Conversion decay, in which the converted electron is excited to a bound orbital instead of a continuum orbital, is discussed. General theoretical results are presented for the relation between bound Internal Conversion and continuum Internal Conversion of the nucleus. It is shown that the transition rate for Internal Conversion decay is continuous across the energy threshold between continuum final states and bound final states. Theoretical predictions for decay to bound states of $^{125}\mathrm{Te}$ are consistent with experimental data on Internal Conversion in highly charged ions of this nuclide. \textcopyright{} 1996 The American Physical Society.
Nikolaus P Ernsting - One of the best experts on this subject based on the ideXlab platform.
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femtosecond relaxation of photoexcited para nitroaniline solvation charge transfer Internal Conversion and cooling
Chemical Physics Letters, 2000Co-Authors: Sergey A Kovalenko, R Schanz, V M Farztdinov, H Hennig, Nikolaus P ErnstingAbstract:Abstract The ultrafast relaxation of p -nitroaniline (PNA) in water and acetonitrile is studied experimentally and theoretically. Transient absorption spectra are measured by the pump–supercontinuum probe technique (PSCP) after 50 fs excitation at 400 nm. The relaxation includes several stages with distinct time scales: solvation, intramolecular charge transfer (CT), Internal Conversion and cooling. The spectral evolution before 100 fs reflects mainly solvation with dynamic Stokes shift of 3500 cm −1 in acetonitrile and 4000 cm −1 in water. CT and Internal Conversion are governed by twisting of the –NO 2 group and proceed in water with 120 and 250 fs, respectively. A hot ground state upon Internal Conversion is characterized by an initial temperature of 1400 K. The subsequent solute–solvent energy transfer is characterized by exponential behavior between 1 and 3 ps and by a nonexponential decay at longer delays, the solute cooling time lies in the range 0.85–1.3 ps.
Eli Pollak - One of the best experts on this subject based on the ideXlab platform.
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On-the-fly semiclassical study of Internal Conversion rates of formaldehyde.
The Journal of chemical physics, 2013Co-Authors: Reuven Ianconescu, Jörg Tatchen, Eli PollakAbstract:Internal Conversion is an inherently quantum mechanical process. To date, "ab initio" computation of Internal Conversion rates was limited to harmonic based approximations. These are questionable since the typical transition to the ground electronic state occurs at energies which are far from the harmonic limit. It is thus of interest to study the applicability of the Semiclassical Initial Value Representation (SCIVR) approach which is in principle amenable to "on the fly" studies even with "many" degrees of freedom. In this work we apply the Herman-Kluk-SCIVR methodology to compute the Internal Conversion rates for formaldehyde for a variety of initial vibronic states. The SCIVR computation gives reasonable agreement with experiment, while the harmonic approximation typically gives rates that are too high.
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semiclassical initial value representation study of Internal Conversion rates
Journal of Chemical Physics, 2011Co-Authors: Reuven Ianconescu, Eli PollakAbstract:Internal Conversion is an inherently quantum mechanical process. To date, “on the fly” computation of Internal Conversion rates is limited to harmonic approximations, which would seem to be especially unsuitable, given that the typical transition to the ground electronic state occurs at energies which are far from the harmonic limit. It is thus of interest to study the applicability of the semiclassial initial value representation (SCIVR) approach which is in principle amenable to on the fly studies even with “many” degrees of freedom. In this paper we study the applicability of the Herman-Kluk (HK) SCIVR to a model system with two coupled and anharmonic degrees of freedom. We find that (a) the HK SCIVR is a good approximation to the exact quantum dynamics; (b) computation of the first order correction to the HK-SCIVR approximation corroborates the accuracy; (c) by studying a large parameter range, we find that the harmonic approximation is mostly unsatisfactory; and (d) for the specific model used, the coupling between the modes was found to be relatively unimportant. These results imply that the HK-SCIVR methodology is a good candidate for on the fly studies of Internal Conversion processes of “large” molecules.Internal Conversion is an inherently quantum mechanical process. To date, “on the fly” computation of Internal Conversion rates is limited to harmonic approximations, which would seem to be especially unsuitable, given that the typical transition to the ground electronic state occurs at energies which are far from the harmonic limit. It is thus of interest to study the applicability of the semiclassial initial value representation (SCIVR) approach which is in principle amenable to on the fly studies even with “many” degrees of freedom. In this paper we study the applicability of the Herman-Kluk (HK) SCIVR to a model system with two coupled and anharmonic degrees of freedom. We find that (a) the HK SCIVR is a good approximation to the exact quantum dynamics; (b) computation of the first order correction to the HK-SCIVR approximation corroborates the accuracy; (c) by studying a large parameter range, we find that the harmonic approximation is mostly unsatisfactory; and (d) for the specific model used, the c...
Toshinori Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast Internal Conversion and Solvation of Electrons in Water, Methanol, and Ethanol
The journal of physical chemistry letters, 2019Co-Authors: Shutaro Karashima, Yo-ichi Yamamoto, Toshinori SuzukiAbstract:Ultrafast Internal Conversion from the first excited state of a solvated electron in water, methanol, and ethanol is investigated using time-resolved photoelectron spectroscopy of liquid microjets and a spectral retrieval method. Photoelectron spectra corrected for inelastic scattering clearly reveal well-separated signals from the excited and ground states, and the latter enables us to analyze the solvation dynamics in the ground state after Internal Conversion. Measurements with 25 fs time resolution identify a rapid increase in the vertical electron binding energy of the solvated electron owing to nuclear wave packet motions in the excited state and allow us to precisely determine the Internal Conversion time.
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Time-Energy Map of Photoelectron Angular Anisotropy for Investigation of Ultrafast Internal Conversion
International Conference on Ultrafast Phenomena, 2010Co-Authors: Takao Fuji, Y. Suzuki, Takuya Horio, Toshinori SuzukiAbstract:Ultrafast Internal Conversion of pyrazine through a conical intersection was observed by photoelectron imaging with 22 fs time-resolution. The 2-D time-energy map of the photoelectron angular anisotropy revealed a clear signature of the Internal Conversion.