Secondary kinetic deuterium isotope effects on unimolecular cleavage reactions: Zero‐point vibrational energy and qualitative RRKM theory

Abstract Observed fundamentals in infrared spectra of pure liquids are red-shifted by the so-called "dielectric effect". This dielectric shift is an excited state effect, and the observed fundamentals must be corrected before one deduces the isotope effects on the zero-point vibrational energy which are needed in the theoretical evaluation of vapor pressure isotope effects. A simple formula is applied to calculate the dielectric shift, which requires only the molar concentration and the integrated absorption coefficient for the fundamental.

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ON THE NECKING-IN PROCESS IN CLUSTER DECAYS

International Journal of Modern Physics A ◽

10.1142/s0217751x90001677 ◽

1990 ◽

Vol 05 (20) ◽

pp. 3901-3928 ◽

Cited By ~ 10

Author(s):

K. DEPTA ◽

J. A. MARUHN ◽

HOU-JI WANG ◽

A. SĂNDULESCU ◽

W. GREINER ◽

...

Keyword(s):

Potential Energy Surfaces ◽

Vibrational Energy ◽

Correction Term ◽

Zero Point ◽

Alpha Decay ◽

Shell Correction ◽

Macroscopic Models ◽

Excellent Description ◽

Energy Surfaces ◽

Zero Point Vibrational Energy

Two new macroscopic models (liquid drop and Yukawa-plus-exponential) describing the decays with emission of large fragments including alpha decay are developed. The proposed shape parametrization consists of two intersecting spheres smoothly joined by a third "rolling sphere". The first two spheres describe asymptotically the charge and mass asymmetries and the third one the necking-in process. It is shown that the potential energy surfaces in the neck and the relative distance between the centers of the spheres (for a given mass and charge fragmentation) lead to different dynamical paths depending on the mass and charge of the emitted fragment. Along the path a phenomenological shell correction term and a zero point vibrational energy are introduced. It is shown that this model gives an excellent description of the present experimental data.

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XZP + 1d and XZP + 1d-DKH basis sets for second-row elements: application to CCSD(T) zero-point vibrational energy and atomization energy calculations

Journal of Molecular Modeling ◽

10.1007/s00894-012-1409-0 ◽

2012 ◽

Vol 18 (9) ◽

pp. 4081-4088 ◽

Cited By ~ 3

Author(s):

Cesar T. Campos ◽

Francisco E. Jorge ◽

Júlia M. A. Alves

Keyword(s):

Vibrational Energy ◽

Zero Point ◽

Atomization Energy ◽

Basis Sets ◽

Energy Calculations ◽

Zero Point Vibrational Energy

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Unusual origins of isotope effects in enzyme-catalysed reactions

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2006.1875 ◽

2006 ◽

Vol 361 (1472) ◽

pp. 1341-1349 ◽

Cited By ~ 23

Author(s):

Dexter B Northrop

Keyword(s):

High Pressure ◽

Isotope Effects ◽

Heavy Atom ◽

Zero Point ◽

Protein Domain ◽

Enzymatic Reactions ◽

Volume Changes ◽

Mass Unit ◽

Deuterium Isotope Effects ◽

Domain Motions

High hydrostatic pressure is a neglected tool for probing the origins of isotope effects. In chemical reactions, normal primary deuterium isotope effects (DIEs) arising solely from differences in zero point energies are unaffected by pressure; but some anomalous isotope effects in which hydrogen tunnelling is suspected are partially suppressed. In some enzymatic reactions, high pressure completely suppresses the DIE. We have now measured the effects of high pressure on the parallel 13 C heavy atom isotope effect of yeast alcohol dehydrogenase and found that it is also suppressed by high pressure and, similarly, suppressed in its entirety. Moreover, the volume changes associated with the suppression of both deuterium and heavy atom isotope effects are virtually identical. The equivalent decrease in activation volumes for hydride transfer, when one mass unit is added to the carbon end of a scissile C–H bond as when one mass unit is added to the hydrogen end, suggests a common origin. Given that carbon is highly unlikely to undergo tunnelling, it follows that hydrogen is not doing so either. The origin of these isotope effects must lie elsewhere. We offer protein domain motions as a possibility.

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