NBOHCNon-Bridging Oxygen Hole Centers
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In absorption spectra, the absorbance of NBOHC increased with the laser power and/or number of laser pulses in vacuum.
The authors accepted that some cathode luminescence emission bands are related to defects: NBOHC with 650 nm (1.9 eV) red-luminescence, the blue and UV bands 460 and 290 nm (2.7 and 4.3 eV) with the Si related oxygen deficient center (Si-ODC).
The E' center, twofold coordinated Si, the neutral oxygen vacancy, and the nonbridging oxygen hole center (NBOHC) are well known centers related to the emission of light in quartz.
One possible cracking site could have been nonbridging-oxygen hole centers (NBOHCs) [25], if any were present.
The facts are that (i) the most radiation-hard nonlaser silica-based optical fibers employ little or no cationic dopants, (ii) the commonly used fluorine dopants appear not to take part in color-center formation [31] (though chloride impurities are problematic [31]), and (iii) for dose rates ~6 Gy/s the transient optical absorption near 660 nm induced at short times in low-OH pure-silica fibers (due to STHs; see below) is ~3 orders of magnitude greater than that of the concomitantly induced 620 nm band of (nondecaying) NBOHCs following atotal dose of [10.sup.7] Gy [31].