Investigation of γ‐irradiation dependent structural properties of LLM‐105 by ultraviolet‐visible diffuse reflectance spectroscopy

Abstract In this work, different doses of γ‐irradiation were applied to 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) to examine the way in which their optical properties and electronic structure can be affected. The UV absorption spectrum of LLM‐105 was calculated based on the time‐dependent density functional theory (TD‐DFT). The analyses of hole‐electron distribution and charge‐transfer spectra (CTS) revealed the type of electronic transitions and elucidated the nature of each excited state in the LLM‐105 molecule. For the pristine LLM‐105, the band gap (E g ) value of 2.76 eV was obtained using the Kubelka‐Munk model. Moreover, the band gap of LLM‐105 increased with the irradiation dose. The increase in relevant UV‐Vis absorption peak intensity, implying the increase in band gap is due to the formation of a larger conjugated structure in LLM‐105 under γ‐irradiation.