ADAMAS GEMOLOGICAL LABORATORY publishes gemologically oriented software for the jewelry appraiser, jeweler, or student in gemology or mineralogy. The laboratory also provides technical consulting and jewelry appraisal services to the trade and the public and expert witness services to the legal profession.

SAS2000: Developed, Produced And Supported In The USA   Questions, Comments, Product Support

Data taken with the SAS2000 Raman/Photoluminescence System had apparently revealed some inconsistancies with the Gubelin Laboratory's report on GEPOL processed diamonds which should be noted, as it appears that relying on the Gubelin article may create a misconception as to whether a diamond has been HPHT treated or not.  On page 212 the authors state: " 514/532 nm Excitation:  At low temperatures the presence of 558.8, 566.8 and 569 nm peaks as well as the series of PL bands between 600 and 620 is a good indication that the diamond has not received HPHT processing.".
NOTE:  I was in error with regards to the 613nm feature, and after a very good conversation with the Gubelin authors, in which I apologized profusely, had a long, and I feel, productive discussion on the GEPOL topic.  We agreed to cooperate and share future information, for the benefit of the industry in understanding this problem area, as we both have complimentary data sources.

We were loaned two GEPOL diamonds by Antoinette Matlins, a 0.95 ct Oval (GEPOL 20186) and a 0.98 ct oval (GEPOL 20969), both E color VVS1 clarity.  Both diamonds revealed, at room temperature and at liquid nitrogen temperature using SAS2000 Liquid Nitrogen Immersion Spectroscopy ( LNIS) techniques, the presence of a strong photoluminescence feature* (not two phonon Raman) at 613 nm when excited with  SAS2000 532 nm Raman/Photoluminescence System excitation.  This is in contradiction with the conclusions drawn in the referenced article as well as published in Tables 2 and 3 as well as in Figures 9** and 10** of that report. Figure P1 below (erroneously supported)supports our conclusions.  Both diamonds showed evidence of a weak 575 nm neutral NV center with no detectable 637 nm feature.

*NOTE   Konstantin Iakoubovskii kindly pointed out to us that the 613nm correlates with a second order Raman intrinsic to diamond and having nothing to do with GEPOL.    Table P1 gives the approximate positions of the two phonon raman peaks with 514.5 (Note that Argon Ion lasers emit at both at 514.18  and 514.53 nm excitation.)

**NOTE  Figures 9 and 10 of the article are labeled 514/532 nm laser excitation.  This appears to be incorrect as the data presented there is apparently ONLY 514nm data as evidenced by the two phonon Raman shown in the 560-595nm region. This adds to the confusion.

We tabulated all the one and two phonon raman features and did a literature search to ascertain the source of the features presented in the Gubelin article and present this data in Table 3.
 

Adamas Gemological Laboratory conducted a Raman/photoluminescence comparison study on three GEPOL (now Bellataire) HPHT processed near colorless diamonds in the SAS2000's permanent collection. For comparison purposes, three SAS2000 calibration GIA/GTL certified diamond master stones of comparable body color were simultaneously run for comparison purposes.

At present we do not have FTIR data to properly categorize and type the six stones in the study. We do however show the six diamonds simultaneously in the SAS2000 Type IIa Short Wave Detector box, which utilizes a 254nm short wave UV source and a Calcium Tungstate (in a proprietary SW transparent binder) fluorescent plate to help determine the Short Wave transparency characteristics of the subject diamonds.  Shown in Figure 1 are the six subject diamonds in the following order.

The three GEPOL diamonds appear to exhibit short wave transparency as shown by the fluorescence under the tables and therefore would be categorized as either Type IIa or Type IaB diamonds, both categories of which exhibit short wave transparency according to the literature.
 

The room temperature Vis-Near IR comparison spectra of the six diamonds are shown in Figures 2 through 4, showing the apparent Type Ia nature (415nm N3 aggregates) of the three diamonds in Master Set #4981 and the "apparent" Type IIa/IaB nature (no indication of aggregated nitrogen) of the General Electric processed near colorless diamonds.
 
 

The Gubelin study (Gems & Gemology Fall 2000 Table 3) of pre/post HPHT processed type IIa diamonds indicated photoluminescence features were seen Pre HPHT in all the PL feature locations shown in Table 3 (all features were not necessarily found in a single diamond).   The "possible source of feature" column are the results of an SAS2000 Diamond Spectral Library Database search, cross referenced data sourced primarily from Zaitsev's Optical Centers chapter in the "Handbook of Industrial Diamonds and Diamond Films" and data from texts by Field, Wilkes, Berman, Burton, Orlov and Davies as well as papers in "Diamonds and Related Materials"

KEY Below:
A  Absorbance
PL  Photoluminescence
CL  Cathodeluminescence
B   Boron
Br   Brown Diamond
CVD  Chemical Vapor Deposition
ION  Ion deposition
R  Radiation
Heat   High Temperature
ZPL   Zero Phonon Line
1PHR  One Phonon Raman
2PHR  Two Phonon Raman
 
 
 

SAS2000 Liquid Nitrogen Immersion Spectroscopy (LNIS) techniques were utilized to obtain low temperature spectra (77 degrees Kelvin) on the three GE POL Diamonds, none of which exhibited any discernible color center / optical defect in the 400 to 1000nm range.

Currently, the SAS2000 Raman / Photoluminescence System offers three types of lasers, a conventional Argon-Ion xxxxx 514nm (also 488,etc) and two diode pumped semiconductor lasers operating at approximately 532nm and at approximately 405nm, each providing approximately 25 milliwatts peak power to the sample.  The 1332cm-1 diamond raman shift signal will appear at the following wavelengths, dependent on the laser selected. Photoluminescence induced signals will always appear at the same wavelength (in nanometers) regardless of laser excitation. In a Raman Shift display mode the PL induced peaks will appear at different  Raman Shift wavenumbers, dependent on the excitation wavelength utilized.
 
 

Power Technology loaned us newly available 405nm semiconductor laser for SAS2000 evaluation. This is a new diode pumped semiconductor laser which produced approximately 25 milliwatts of power as measured by a Coherent LaserCheck detector. It appears to produce a power doublet at 402.7nm and 405.2nm which results in a slightly smeared and wider photoluminescence response, however the data were still very usable.