Upon excitation at 170−240 nm, diamonds emit strong
luminescence in wavelength range of 300−700 nm. The spectral features
observed in the photoluminescence excitation (PLE) spectra show two
vibrational progressions, A and B, related to nitrogen defects N2 and N4,
respectively. We used PLE spectra excited in region 170−240 nm to identify the
type of diamond and demonstrate quantitative analysis of the B center as a N4
nitrogen defect in diamonds; the least detectable concentration of the N4
nitrogen defect is about 13 ppb, and the sensitivity of PLE is about 30 times than
that practicable with infrared absorption spectra.