The process and apparatus introduce a carrier gas into a vacuum evaporation chamber, evaporate a film forming material from a evaporation source and deposit the evaporated film forming material on a substrate in sheet form to form a stimulable phosphor layer, thereby producing a evaporated phosphor sheet having a stimulable phosphor layer formed on the substrate. The stimulable phosphor layer is formed with substantially all areas of the evaporation source except opening for evaporation being masked to block movement of heat toward the substrate. The evaporated phosphor sheet includes the substrate and a CsBr:Eu evaporated stimulable phosphor layer deposited on the substrate. A maximum intensity of instantaneous light emission from the stimulable phosphor layer at 640 nm upon excitation by uv radiation is lower than a maximum intensity of the instantaneous light emission at 440 nm.