2006ApJ...639L..63C

Diamond nanocrystals (size ∼100 nm) emit bright luminescence at 600-800 nm when exposed to green and yellow photons. The photoluminescence, arising from excitation of the nitrogen-vacancy defect centers created by proton-beam irradiation and thermal annealing, closely resembles the extended red emission (ERE) bands observed in reflection nebulae and planetary nebulae. The central wavelength of the emission is ∼700 nm, and it blueshifts to ∼660 nm as the excitation wavelength decreases from 535 to 470 nm as the result of a combined excitation of two different detect centers [(N-V)^– and (N-V)⁰]. Our observations lend support to the suggestion that nanodiamond is a possible carrier for the ERE band.