The shifts of the first two exciton peaks with hydrostatic pressure have been measured in CsI films at 78°K and found to be linear. The deformation potentials deduced are -2.10 eV and +2.10 eV, respectively. These results confirm Onodera's assignment of the two peaks to excitons derived from bands of different symmetry. The data indicate that above 7 kbar the conduction bands cross and the Γ12 level lies below the Γ1 (Onodera's assignment).
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