Energy levels of the 603/700/787 nm luminescence system in natural diamond

A study was carried out of the photoluminescence system 603/700/787 nm in a natural diamond crystal at a temperature range of 77 – 300 K. In the emission spectra, two zero-phonon lines 584 and 603 nm appear at 300 K. Phonon replicas of about 40 and 70 meV assist the lines 656, 700 and 787 nm at 77 K. For the 603 nm zero-phonon line, one phonon replica of 69 meV is observed. The value of Huang–Rhys factor is 1.0, 1.2, and 0.7 for the corresponding lines 603, 700, and 787 nm: it indicates the middle level of the electron-phonon interaction. According to the excitation spectra, three exited energy levels were revealed: 2.86 eV for 656 and 700 nm, 2.68 eV for 584 and 603 nm, and 2.49 eV for 787 nm. The pairs of lines 584/603 and 656/700 nm can be interpreted as spin-allowed and forbidden electronic transitions, respectively.