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Two-electron exchange in collisions of neutral molecules (1993)

Drakes, James. A. ; McGregor, Wheeler K. ; Mason, Arthur A.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 99 (1993), S. 7813-7818

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The quenching behavior of neutral metastable species during collisions with a neutral partner is investigated. Usually, radiationless energy transfer can be described by invoking the radiation field as an intermediary between interacting molecules. However, for metastables, the dominant radiation transition moments are suppressed, most often by spin selection rules between the excited and ground energy states. The fast reaction rates for the quenching of the metastables suggest a different intermediary for such cases. Motivated by this phenomena, a two-electron exchange process is proposed as the quenching mechanism. During a collision, it is envisioned that the excited outer shell electron of the metastable effectively undergoes a change of molecular center and is replaced by an electron from the collision partner. The theoretical framework for this process is developed using the formalism of molecular quantum electrodynamics. The electron exchange term is obtained explicitly, using the minimal-coupling method.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.465659

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Radiation-induced cytotoxicity, DNA damage and DNA repair: Implications for cell survival theory (1990)

Swarts, S. G. ; Nelson, G. B. ; Wallen, C. A. ; [et al.]

Springer

Radiation and environmental biophysics 29 (1990), S. 93-102

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ISSN: 1432-2099

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Physics

Notes: Summary The radiosensitivities and the kinetics for removal of radiation-induced DNA damage were compared for proliferative (P) and quiescent (Q) cells of the lines 66 and 67 derived from a mouse mammary adenocarcinoma. As determined from cell survival assays, the 66 and 67 Q cells were more radiosensitive than their 66 and 67 P counterparts. The rank order of their radiosensitivity was: 67 Q 〉 66 Q ≥ 67 P 〉 66 P. Induction of radiation damage in the DNA of these cells, as measured by the alkaline elution technique, was identical for 66 and 67 P and Q cells. The repair of this DNA damage was biphasic for 66 and 67 P and Q cells. The half-times for the fast and slow repair phases in 66 Q cells were identical to those previously measured in 67 Q cells. The half-times of the fast and slow repair phases in 66 P cells were also identical to those previously measured in 67 P cells. However, the half-times for the fast and slow repair phases in 66 and 67 Q cells were longer than those measured in their 66 and 67 P counterparts. The 66 cell data are consistent with our previously published hypothesis that Q cells are more radiosensitive than their corresponding P cells because they repair their radiation-induced DNA damage slower. However, our results are not consistent with hypotheses that attempt to explain the radiosensitivity differences between lines 66 and 67 solely on the basis of measurable induction and repair of DNA damage.