Creation of nanosize defects in LiF crystals under 5- and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>10</mml:mn><mml:mtext>−</mml:mtext><mml:mi>MeV</mml:mi></mml:mrow></mml:math>Au ion irradiation at room temperature

Investigation of radiation defects induced by the irradiation of LiF crystals with 5- or $10\text{\ensuremath{-}}\mathrm{MeV}$ Au ions (fluences of ${10}^{11}--2\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}\text{ions}∕{\mathrm{cm}}^{2}$; flux varies by 2 orders of magnitude) at room temperature has been performed using the methods of optical absorption and high-temperature $(400--750\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ thermoactivation spectroscopy. The creation efficiency of color centers $(F,{F}_{2},{F}_{3},\dots{})$ and colloids drastically depends on both the fluence and ion flux (beam current). Besides impurity (magnesium) colloids with the absorption band peaked at $4.4--4.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, the broad absorption band at $2.3--3.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ related to intrinsic Li colloids is reliably distinguished. The creation efficiency of Li colloids by $5\text{\ensuremath{-}}\mathrm{MeV}$ Au ions is lower than that by $10\text{\ensuremath{-}}\mathrm{MeV}$ ions, which form $\ensuremath{\delta}$ electrons with higher energies sufficient for the creation of cation excitons $(\ensuremath{\sim}62\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$. The cation exciton decays, in turn, with the formation of a group of spatially close $F$ centers. At a high ion flux, the next bombarding ions hit the same crystal region with a small time delay $(10--100\phantom{\rule{0.3em}{0ex}}\mathrm{s})$ and also form, after similar intermediate processes, the groups of $F$ centers that participate in the formation of stable agglomerates of several ${F}_{3}$ or even more complex centers, which serve as stable (up to $620\phantom{\rule{0.3em}{0ex}}\mathrm{K}$) seeds for nanosize Li colloids. The peculiarities of the formation, enlargement, and annealing of intrinsic colloids in LiF crystals are considered, invoking a formal analog with the processes in photographic materials based on silver halides.

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