The influence of HTHP treatment on the OK1 and N3 centers in natural diamond crystals

Abstract

The structures of nitrogen-containing paramagnetic centers OK1 and N3 have not been unambiguously determined yet. In this paper, we will present data on the influence of high temperature annealing on the paramagnetic centers OK1 and N3 in diamond. A series of natural colored diamond crystals of cubic habit containing paramagnetic centers OK1 and N3 was studied by electron paramagnetic resonance (EPR), luminescence, and IR spectroscopies. It was found that annealing at temperatures above 2470 K led to the transformation of N3 paramagnetic centers into OK1 paramagnetic centers. Previous work has showed that a temperature in excess of 2400 K are often associated with a local environment change of tetrahedral to octahedral for impurities with large atomic radii. We report a correlation with the intensity of the optical 635.7 nm system and the concentration of the N3 EPR center. However, on stepped annealing 635.7 nm was removed before the N3 EPR center. From the analysis presented, we propose that the N3 EPR center and the 635.7 nm optical system are the manifestation of various defects formed by one impurity atom. 1 Introduction Although the nitrogen-containing paramagnetic centers OK1 and N3 [1, 2] were first detected more than 30 years ago, the identity of these centers was not been unambiguously determined [2][3][4][5]. Regarding the nature of defects in diamond, more than 500 have been characterized with only a handful identified. Of those positively identified, EPR was often a key tool used in unlocking their structure and identity. This includes nitrogen centers P1 [6], P2 [7,8], W7 formed by the interaction of Acenters with the dislocation [9,10], and N 2 V which is the result of the interaction of A-centers with vacancies [10]. In addition, the structures of nickel-nitrogen centers NE1-NE9 [11][12][13][14], boron-nickel centers [15], nitrogen-cobalt centers [16,17], nitrogen-phosphorus centers NP1-NP7 [18][19][20], oxygen-containing [21], and hydrogen-containing centers [22,23] were determined. OK1 and N3 EPR centers remain unidentified but are often observed together, as shown by recent studies [23]. They are a characteristic

Specific spectroscopic features of yellow cuboid diamonds from placers in the north-eastern Siberian Platform

“…This centre has previously been detected in many yellow cuboid diamonds (Zudina et al 2013;Zedgenizov et al 2016). The correlation between the 635.7 nm luminescence system and the N3 centre detected by EPR has recently been demonstrated by Nadolinny et al (2015). However, although we observed the 635.7 nm system in yellow cuboid diamonds we did not detect the N3 centre with EPR.…”

“…Recently it has been found that in natural diamonds from eclogitic xenoliths the detection of paramagnetic OK1 and N3 centres correlated with the abundance of titanium compounds (Nadolinny et al 2009b(Nadolinny et al , 2012(Nadolinny et al and 2015. The samples with observed OK1 and N3 centres have low total nitrogen concentration of about 10 ppm because the titanium is the nitrogen getter (Nadolinny et al 2012).…”

Incorporation of Large Impurity Atoms into the Diamond Crystal Lattice: EPR of Split-Vacancy Defects in Diamond

“…The analysis of the phonon structure of the N3/440.3 nm center showed that the energy of the quasi-local vibration (53 meV) corresponded to the titanium atom mass [33]. Annealing of natural diamond crystals at 2500 K for two hours showed that the N3 paramagnetic center transformed into OK1 paramagnetic centers [37]. Table 3.…”

Features of the impurity composition of diamonds from placers of the northeastern Siberian craton

“…Общее содержание примесного азота в них колеблется в пределах от 56 до 1200 ppm. По данным ФЛ, в 18 из 25 кристаллов кубического габитуса наблюдается электронно-колебательная система (ЭКС) 635,7 нм [10], в 13 кристаллах присутствуют азотно-титановые центры с эмиссией S1 (OK1 в спектрах ЭПР), и в одном из этих кристаллов наблюдается ЭКС с бесфононной линией (БФЛ) 485 нм, ответственная за проявление парамагнитного азотно-титанового центра NU1 со структурой расщеплённой по <100> межузельной конфигурации [8]. По данным ЭПР в вышеперечисленных 18 кристаллах регистрируется азотно-титановый центр N3.…”

“…Но в отличие от ранее изученных кристаллов алмаза октаэдрического габитуса [8], в кубах из россыпи Исток не регистрируется оптическая система с БФЛ 440,3 нм, ранее отнесённая к проявлению азотно-титанового центра N3. В работе [10] отмечалось, что в кристаллах кубического и кубо-октаэдрического габитуса из других месторождений регистрируются в спектрах ЭПР центры ОК1 и N3, а в люминесценции оптические системы S1 и 635,7 нм. Слабая оптическая система с БФЛ 440,3 нм отмечалась только в пяти кристаллах.…”