Temperature-dependent absorption of biotite; small-polaron hopping and other fundamental electronic excitations
Temperature-dependent absorption of biotite; small-polaron hopping and other fundamental electronic excitations (in The 7th European conference on Mineralogy and spectroscopy, Monika Koch-mueller (editor), Michael Fechtelkord (editor), Vladimir Khomenko (editor) and Sergio Speziale (editor))
European Journal of Mineralogy (September 2012) 24 (5): 817-822
Temperature-dependent absorption investigations between 10 and 823 K reveal photon-assisted hopping (PAH) of small polarons in biotites as the dominating excitation in the near-infrared spectral range. These data show a transfer of oscillator strength of the PAH of small polarons to Fe (super 2+) -Fe (super 3+) intervalence-charge transfer and Fe (super 2+) d-d transitions with decreasing temperature. The loss in oscillator strength of PAH is related to a pinning of the polarons due to the decreasing number in lattice vibrations in thermal equilibrium.