First-principles X-ray absorption dose calculation for time-dependent mass and optical density
| Autor: | Lis G. A. Melo, Boris Rubinstein, Viatcheslav Berejnov, Adam P. Hitchcock |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Physics
Nuclear and High Energy Physics Radiation 010304 chemical physics Kinetics X-ray 02 engineering and technology Function (mathematics) Photon energy 021001 nanoscience & nanotechnology 01 natural sciences Exponential function 0103 physical sciences Microscopy Radiation damage Atomic physics 0210 nano-technology Absorption (electromagnetic radiation) Instrumentation |
| Zdroj: | Journal of synchrotron radiation. 25(Pt 3) |
| ISSN: | 1600-5775 |
| Popis: | A dose integral of time-dependent X-ray absorption under conditions of variable photon energy and changing sample mass is derived from first principles starting with the Beer–Lambert (BL) absorption model. For a given photon energy the BL dose integralD(e, t) reduces to the product of an effective time integralT(t) and a dose rateR(e). Two approximations of the time-dependent optical density,i.e.exponentialA(t) =c+aexp(−bt) for first-order kinetics and hyperbolicA(t) =c+a/(b+t) for second-order kinetics, were considered for BL dose evaluation. For both models three methods of evaluating the effective time integral are considered: analytical integration, approximation by a function, and calculation of the asymptotic behaviour at large times. Data for poly(methyl methacrylate) and perfluorosulfonic acid polymers measured by scanning transmission soft X-ray microscopy were used to test the BL dose calculation. It was found that a previous method to calculate time-dependent dose underestimates the dose in mass loss situations, depending on the applied exposure time. All these methods here show that the BL dose is proportional to the exposure timeD(e, t) ≃K(e)t. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|