Luminescence of diamond

The luminescence of diamonds is related to various defects in its structure. Almost always, luminescence centers in diamonds are related to N atoms. It is logical, because the atomic radii of C and N are nearly equal (approximately 0.77 A). Luminescence spectroscopy has proven to be the most widely used method in studies of diamonds even in comparison with optical absorption, ESR, IR and Raman spectroscopies. Himdreds of spectra have been obtained, fluorescence characteristics enter into diamond quality gemological certificates, a wide range of electronic and laser applications are based on diamond optical properties in excited states nitrogen center aggregation is controlled by the residence time of diamond in the mantle, distinction between natural... 

Our study of time-resolved luminescence of diamonds revealed similar behavior (Panczer et al. 2000). Short-decay spectra usually contain N3 luminescence centers (Fig. 4.71d 5.69a,b) with decay time of r = 30-40 ns. Despite such extremely short decay, sometimes the long-delay spectra of the same samples are characterized by zero-phonon lines, which are very close in energy to those in N3 centers. At 77 K Aex = 308 nm excitation decay curve may be adjusted to a sum of two exponents of ti = 4.2 ps and i2 = 38.7 ps (Fig. 5.69c), while at 300 K only the shorter component remains. Under Aex = 384 nm excitation an even longer decay component of 13 = 870 ps may appear (Fig. 5.69d). The first type of long leaved luminescence may be ascribed to the 2.96 eV center, while the second type of delayed N3 luminescence is ascribed to the presence of two metastable states identified as quarfef levels af fhe N3 cenfer. 

It demonstrates that time-resolved luminescence of diamond is much more informative for ID task than the steady-state one. Vast amount of luminescence centers are known in natural diamonds (Zaitsev 2005) and if the specific diamond... 

Determination of tint is the essential and the most intricate aspect in diamonds evaluation and may be useful for luminescence interpretation. The coloration of diamond is a reflection of its complex structural pecuharity. To describe a slight shade of color, one has to use a lot of physics, crystallography and analytical tools. The following types of diamond coloration are generally distinguished. 

Fig. 4.71. a-d Laser-induced time-resolved luminescence spectra of diamonds demonstrating N3, A, and H3 centers... 

Fig. 4.72. a-f Laser-induced steady state luminescence spectra of diamonds demonstrating S3, S2, H3, GRl, 700, 788 and possibly 640 nm... 

The H3 center is well known in the steady-state luminescence spectra of diamonds. It belongs to the C2v point group, the ground state being level and the excited state from which luminescence takes place a Bi. Both emis-... 

At the present time luminescent sorters are mainly used for the processing of diamonds, but also for the scheehte, fluorite and others types of ores (Mokrousov and lileev 1979 Salter and Wyatt 1991 Gorobets et al. 1997a). The sources of luminescence excitation in these sorters are X-ray tubes and UV lamps, where the first is more powerful and the second is more selective. The UV impulse lasers employment as excitation sources enables us to combine the... 

Diamond luminescence was studied mainly with the two following aims to carry out a fundamental investigation of its physical properties and to determine the optimal conditions for luminescent sorting of diamond bearing rocks. For the first task, diamond photoluminescence was studied at liquid nitrogen temperature at which luminescence centers are marked by characteristic zero-phonon fines and are much more informative then at room temperature. For the second task, were diamond is one of the first minerals for which luminescence sorting was used, liuninescence properties should be studied at 300 K. In the first stages it was established that X-ray luminescence of the A-band... 

The luminescence properties of nanoscale diamond have as well been subject to extensive study. For nanoscopic particles, as compared to the respective bulk material, deviating characteristics are generally expected due to the large portion of surface atoms and a potentially distorted band structure. Yet for diamond, the bandgap is unaffected by particle dimensions (at least in the relevant range), and the luminescence of the nanomaterial has many features in common with that of the bulk phase. 

Moreover, an application on biochips for the determination of certain proteins in a serum has been presented. The attachment takes place, for instance, on an immobilized enzyme with the read-out of information normally being enabled by fluorescence labeling. Besides an external fluorescence label, it is also possible to employ the inherent luminescence of lattice defects in the diamond itself (Section... 

The luminescence characteristics of diamond films are also strongly affected by the presence of defects. Although it requires considerable energies, an excitation across the entire bandgap is possible. It may be effected by (laser) light, by an... 

Diamond is the best optical material available and this lack of absorbance accounts for its unique brightness. However, no diamond is perfect and lattice defects combined with impurities, such as nitrogen and boron, give visible coloration and can also cause luminescence. The high cost of diamond has almost completely restricted its use in optical applications. 

The spectroscopic method is based on pressure-induced changes in absorption or/and emission spectra. The idea is to relate the pressme-induced shift of the fluorescence lines of the specific material to the value of the pressure. The material selected for the luminescence pressure sensor should be characterized by strong intensity of the emission line(s), which should be stable at a broad range of pressures and temperatures and the energy of which is possibly related linearly to pressure. It is also important that the emission of the sensor does not overlap the emission of the sample. Considering the above-mentioned requirements, the Raman fluorescence and photoluminescence of transition-metal and rare-earth ions were used. Raman modes of nitrogen [49], which is the pressure-transmitting medium, and Raman frequencies of diamond chips [51] have been used. Recently, a pressure-induced shift of the Raman line 1332 cm of the face of the DAC culet was proposed to estimate pressure < 1,000 kbar [50, 52]. 

Visible luminescence is a well-known optical property of single crystal diamond particularly in the blue and green regions. This luminescence originates in the states at mid-bandgap and is caused by impurities and lattice defects. Cathodoluminescence (CL) is another characteristic of diamond. The CL of single crystal diamond is described as a band-A luminescence and the peak of the spectra is found between 2.4 and 2.8 eV (from green to purple-blue).f 2M lf J... 

Kimberliteisthe principal diamond bearing ore. In atypical mine such as the Premier Mine near Pretoria, South Africa, one hundred tons of kimberlite produce an average of thirty-two carats of diamond (6.4 g). Dieimonds are sorted from the mineral by an x-ray beam the diamond luminesces with the x-ray and the luminescence activates an air Jet which propels the diamond into a separate bin (Fig. 12.1).i ] Gemstones (a very small percentage) are then separated from the industrial-quality material. 

BenstockE, BuseckP, Steele 1 (1997) Cathodoluminescence of meteoritic and synthetic forsterite at 296 and 77 K using TEM. Am Mineral 82 310-315 Blasse G (1980) Luminescence and energy transfer. Struct Bond 42 1 1 Blasse G, Aguilar M (1984) Luminescence of natural calcite (CaC03). J Lumin 29 239-241 Bokii G, Bezrykov G, Khyev Yu et al (1986) Natural and synthetic diamonds. Nauka, Moscow (in Russian)... 

Lenz C, Nasdala L, Talla D et al (2015) Laser-induced REE " photoluminescence of selected accessory minerals - an advantageous artefact in Raman spectroscopy. Chem Geol Lupashko T, Tarashchan A, Kvasnytsya V et al (1996) Luminescence, EPR and morphology of diamond crystals from placer deposits. In Abstracts of third European meeting Spectroscopic Methods in Mineralogy , Kiev, 10-13 p 27... 

Walker J (1979) Optical absorption and luminescence in diamond. Rep Progr Phys 42 1605-1659 Walker G, Kamaluddin B, Glynn T, Cherlock R (1994) Luminescence of Ni centers in forsterite (Mg2Si04). J Lumin 60 61 123-126... 

The N3 optical center is one of the best known in steady-state luminescence spectra diamond. It is connected with three substitutional nitrogen atoms botmded to a common carbon atom or a vacancy, the ground state being a level and the excited state where luminescence originates a state (C3V point group). The zero-phonon line occurs at 2.985 eV and absorption and emission spectra show very closely a mirror relationship (Bokii et al. 1986). The N3 prompt luminescence decay is exponential and equal to 40 ns. Time-resolved luminescence spectroscopy enables to detect that N3 center has some metastable levels between the emitting and ground state. One of the decay paths of these metastable levels is delayed N3 luminescence, which occurs... 

---