Broad-band luminescence in natural brown type Ia diamonds

Broad-band luminescence centred at ∼ 1.75 eV (∼ 710 nm) is typically encountered in natural brown type Ia diamonds which show evidence of plastic deformation, particularly when using excitation at 514 nm. The band is comprised of 2 broad sub-bands. One of these bands is clearly a vibronic band, and the Huang–Rhys factor and the one-phonon density of states have been determined. The Huang–Rhys factor of S = 8.0 ± 0.5 is relatively high for diamond, and the one-phonon density of states is composed of 2 moderately sharp peaks at 17 and 44 meV.