科研之友
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摘要
The problem of absolute measurements of radiation damage in films of nanometer thicknesses is addressed. Thin films of DNA (approximate to 2160 nm) are deposited onto glass substrates and irradiated with varying doses of 1.5-keV X-rays under dry N-2 at atmospheric pressure and room temperature. For each different thickness, the damage is assessed by measuring the loss of the supercoiled configuration as a function of incident photon fluence. From the exposure curves, the G-values are deduced, assuming that X-ray photons interacting with DNA deposit all of their energy in the film. The results show that the G-value (i.e. damage per unit of deposited energy) increases with film thickness and reaches a plateau at 305 nm. This thickness dependence provides a correction factor to estimate the actual G-value for films with thicknesses 30 nm thickness. Thus, the absolute values of the damage can be compared with that of films of any thickness under different experimental conditions.
- 出版日期2012-9
