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Titolo:
Coulomb repulsion in multiply charged ions: a computational study of the effective dielectric constants of organic spacer groups
Autore:
Gronert, S;
Indirizzi:
San Francisco State Univ, Dept Chem & Biochem, San Francisco, CA 94132 USASan Francisco State Univ San Francisco CA USA 94132 ancisco, CA 94132 USA
Titolo Testata:
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
, volume: 187, anno: 1999,
pagine: 351 - 357
SICI:
1387-3806(19990429)187:<351:CRIMCI>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
IONIZATION MASS-SPECTROMETRY; GAS-PHASE BASICITIES; ELECTROSPRAY-IONIZATION; CYTOCHROME-C; KINETIC METHOD; IN-VACUO; PEPTIDE; PROTEIN; POLARIZABILITY; STATE;
Keywords:
Coulomb explosion; multiply charged ions; ab initio calculations; dielectric constants;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
30
Recensione:
Indirizzi per estratti:
Indirizzo: Gronert, S San Francisco State Univ, Dept Chem & Biochem, San Francisco, CA 94132 USA San Francisco State Univ San Francisco CA USA 94132 94132 USA
Citazione:
S. Gronert, "Coulomb repulsion in multiply charged ions: a computational study of the effective dielectric constants of organic spacer groups", INT J MASS, 187, 1999, pp. 351-357

Abstract

Using dication and dianion models, effective dielectric constants have been calculated for several organic spacer groups (alkyl, poly-ether, and poly-ketone). Specifically, ab initio calculations at the MP2/6-31+G(d,p)//HF/6-31+G(d) level were used to estimate the Delta H-acid and the proton affinity (PA) values of a series of diammonium and dialkoxide ions, respectively. The variation in these values as a function of the distance between charges leads to the effective dielectric constant (epsilon) of the organic spacer group. For all the spacer groups, effective dielectric constants near unity were obtained indicating that the spacer group does not reduce the Coulomb repulsion in the doubly charged ion (relative to a vacuum). The values obtained in this study are all slightly less than unity (similar to 0.85) because the definition of the charge separation as the distance between the formal charge centers (N or O) neglects delocalization and overestimates thetrue charge separation. For similar reasons, epsilon values slightly less than unity are also appropriate for zwitterionic systems. (C) 1999 ElsevierScience B.V.

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Documento generato il 27/09/20 alle ore 05:58:30