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.

GEPOL

SAS2000: Developed, Produced And Supported In The USA   Questions, Comments, Product Support
Adamas Gemological Laboratory is proud to introduce to the industry the custom built SAS2000 Spectrophotometer Analysis System for diamond and gemstone evaluation and grading. The SAS2000 provides the most accurate colorimetry available today for diamond color grading, helps determine radiation treatments of diamond, provides better ability than the DeBeer's DiamondSure to detect probable  synthetic diamonds , and replaces the spectroscope for transparent gemstone evaluation.
PREFACE
Gems & Gemology Fall 2000
"GEPOL Diamonds: Before and After"
Some Contradictory Data?

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.
 

Table P1 Two Phonon Raman Positions Vs Excitation
Position
Raman Shift
cm-1
244nm 325nm 402.7nm 405.2nm
514.18nm
514.53nm
532.0nm
1864
255.63 345.96 435.38 438.3
568.68
569.11
590.56
2178
257.69 349.96 441.42 444.42
579.02
579.47
601.72
2256
258.21
581.65
582.10
604.65
2333
258.73
584.27
584.72
607.39
2360
258.91
585.19
585.64
608.38
2370
258.98
585.53
585.99
608.75
2460
259.58
588.84
589.09
612.11
2467
259.63
588.88
589.34
612.37
2491
259.79
589.71
590.17
613.27
2501
259.86
590.06
590.52
613.65
2519
259.98
590.69
591.15
614.33
2667
260.98 355.84 451.15 454.29
595.90
590.37
619.96

 
 
 
 

Figure P1 GEPOL 20969 E VVS1 0.98 Oval

In Process Study Follows
GEPOL HPHT PHOTOLUMINESCENCE STUDY

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.

Table 1
 
GIA/GTL Reference 
 Size
Color Grade 
(AGS est CM)
 
Master Set 4981-1
0.39ct RBC
E (0.60*)
 
Master Set 4981-2
0.36ct RBC
H (2.15*)
 
Master Set 4981-4
0.32ct RBC
K(3.50*)
 
GIAGTL #00000000
RBC
E(**)
 
GIAGTL #10529099
0.29ct RBC
H(**)
 
GIAGTL #10646307
0.41ct RBC
K(**)
 
* GIA/GTL Estimate
** SAS2000 Colormetric Estimate

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.

Table 2

4981-1 E
4981-2 H
4981-4 K
00000000 E
10529099 H
10646307 K

Figure 1

















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.
 
 

Figure 2

Figure 3

Figure 4
 
 
 
 
 
 
 
 
 
 
 
 
 
 

GEPOL HPHT Raman/Photoluminescence Features
Prelimiminary

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
 
 
 

Table 3 GEPOL Raman Photoluminescence Features
System
Laser Wavelength
Used to Observe
Feature
PL Feature
Type IIa
Post HPHT
Gubelin
325/514/532
Type IIa
Post HPHT
SAS2000
405/514/532
Type Ia

SAS2000
405/514/532

Possible
Source Of  Feature
Closest Reference
 
244
251.1
      250.93(1132cm-1)[244].....1PHR
251.36(1200cm-1)[244].....1PHR
 
244
254.2
      253.91(1600cm-1)[244].....1PHR
254.11(1630cm-1)[244].....1PHR
255.30(4.855eV)................CL
 
244
256.2
      255.78(4.846eV)................CL
256.51(4.832eV)................
256.52(4.832eV)................CL
 
244
257.3
      257.69(2178cm-1)[244].....2PHR
256.63(4.830eV)................CL,CVD
 
244
263.9
                       2BD(G) Center
263.84(4.698eV)...ZPL,A,CLB,R.

264.29(4.690eV)...............A,PL

 
244
265.1
      265.08(4.676eV)......ZPL, CL,R
 
244
267.3
      267.13(4.640eV)..........CL, CVD
267.19(4.639eV)..........ZPL,CL,R
 
244
277.4
      277.42(4.468eV).........A
 
244
286.0
      286.39(4.328eV)...A,R
 
244
291.6
      290.28(4.270eV).............A
 
244/325
404.8
                      H9 Center
 404.80(3.062eV).............A
 
244/325
406.0
                      R9 Center 
407.73(3.040eV)......A,PL,ZPL,R
 
325
409.6
x
 
 
No Reference Found
 
325
412.3
x
 
 
GR8e
412.34(3.006eV)...........A,CL,PL,R 
N3
244/325
415.2
x
 
 
N3 Center
415.20(2.985eV)...N3........................
415.24(2.985eV)..........CL,ZPL,CVD
 
244/325
417.2
x
 
 
417.20(2.971eV).................ZPL,PL 
 
325
421.0
x
 
 
GR5 Center 
421.60(2.940eV)    ...A,CL,PLR
 
325
423.0
 
 
 
 H6 Center
423.76(2.925eV)........A, R
 
325
428.0
x
 
 
 GR4
427.12(2.902eV)...A,CL,PL,R
429.04(2.889eV).....ZPL,CL,SYN
 
325
430.9
x
 
 
GR2 Center
430.30(2.881eV)........................R
431.28(2.874eV)...........CL,CVD
 
325
439.0
x
 
 
 438.70(2.825eV).........................A
439.54(2.820eV)............. .CL,ION
 
325
441.0
x
 
 
440.32(2.815eV)................ZPL,PL 
441.58(2.815eV)....ZPL,CL,CVD,R
 
325
452.0
x
 
 
 451.05(2.748eV)...................Br,CL
451.00(2.748eV)..........Br, ZPL,CL
453.00(2.736eV)............................
 
325
463.0
x
 
 
462.50(2.680eV).....................ZPL
462.50(2.680eV)...........A,CL,PL,R
463.19(2.676eV)..........CL,CVD 
 
325
478.0
x
 
 
477.83(2.594eV)..................A,PL,R
478.00(2.593eV) ...G&G IaA treated
478.20(2.592eV)........         PL,ZPL
 
325
490.7
 
 
 
 490.40(2.527eV)..........................A
490.70(2.526eV)...........A,CL,PLZPL
490.70(2.526eV)..............................
H4
325
496.1
 
 
 
H4 Center
496.20(2.498eV)....A,CL,PL,ZPL,R
 
325
498.3
 
 
 
497.79(2.490eV)...........BR,PL,ZPL
498.20(2.448eV)........CL,ZPL,ION
H3
325
503.1
x
 
 
 H3 Center
503.20(2.463eV).......A,CL,PL,ZPL,CVD,R,ION
503.4(2.462eV) (H3)........................Br,R 
S1 Center
503.20(2.463eV)...................................PL,ZPL
3H Center
503.45(2.462eV).....................A,CL,PL,ZPL,R
 
324
504.9
 
 
 
 505.00(2.454eV)..G&G emission line
 
325
512.0
 
 
 
 512.00(2.421eV) J.Gemm.........Br
 
325
520.0
 
 
 
 519.70(2.385eV)  Field.....1700C anneal
519.71(2.385eV)...........Cl,ZPL
519.71(2.385eV)...................A
520.14(2.383eV)...J.Appl Phys  Ni 1800C anneal
520.80(2.380)...................A
 
325
528.0
 
 
 
527.45(2.350eV)...........................A
527.45(2.350eV)...................A,ZPL
527.75(500cm-1) [514.18] ..........1PHR
528.12(500cm-1)[514.53]...........1PHR
527.70(521cm-1)[514.53]...........1PHR
*
325/514
535.9
 
 
 
 535.42(2.315eV)................CL,ION
535.88(2.313eV)................A,CL,R
535.90(2.313eV) Field.................R
*
325/514
537.4
 
 
 
537.00(2.308eV) J. Gemm..........Br
537.74(2.305eV)............CL,R,ION
 
514
558.8
 
 
 
 557.58(2.223eV)....................CL,ION
558.50(2.219eV)  J. Gemm..............Br
558.71(1550cm-1)[514.18]........1PHR
559.02(1560cm-1)[514.18].......1PHR
559.27(1568cm-1)[514.18].......1PHR
559.12(1550cm-1)[514.53].......1PHR
560.10(943cm-1)[532.0]...........1PHR
 
514
566.8
 
 
 
 No Reference Found
566.09(1132cm-1)[532.0].......1PHR
 
514
569.0
 
 
 
568.28(1200cm-1)[532.0]............. ..1PHR
568.68(1864cm-1)[514.18].............2PHR
568.93(1220cm-1)[532.0]..............1PHR
569.11(1864cm-1)[514.53]..............2PHR

569.36(2.177eV)................CL,ZPL,ION
569.89(2.175eV).........................PL,ZPL

(N-V)0
325/514/532
574.8
x
 
 
 574.80(2.156eV)................Br,PL,ZPL
574.90(2.156eV)..................................CL
574.90(2.156eV)  Field.... R,Heat
574.90(2.156eV)   G&G ............R
T1 Center
574.91(2.156eV)......A,CL,PL,R,ION
 
325/514/532
575.8
x
 
 
575.8(1430)[532]..Resonant Raman
 
325/514/532
578.8
 
    577.85(2.145eV)..........   ....Br,CL,PL,ZPL 
579.02(2178cm-1)[514.18]................2PHR
579.47(2178cm-1)[514.53]................2PHR
578.14(1500cm-1)[532.0]..................1PHR
578.47(1510)[532] .Resonant Raman
 
532
587.0
 
 
 
586.33(2.114eV)..............Br,PL,ZPL 
587.44(2.110eV).......................CL,B
 
532
596.0
 
 
 
 595.34(2.082eV)..................Br,PL,ZPL
595.90(2667cm-1)[514.18]...........2PHR
596.37(2667cm-1)[514.53]...........2PHR
 
514
600.0
 
 
 
 598.79(2.070eV).............CL,B
601.99(2.059eV)..........CL,ZPL,ION
601.72(2178cm-1)[532.0]............2PHR
 
514
613.0-617.0
 
 
 
612.37(2467cm-1)[532.0].........2PHR
613.27(2491cm-1)[532.0]..................2PHR
 613.61(2.020eV)..............CL,ZPL,ION
613.65(2501cm-1)[532.0]...........2PHR
614.33(2519cm-1)[532.0]...........2PHR
614.70(2.016eV).............CL,ZPL,ION
616.20(2.012eV)...............CL,ZPL,ION
616.67(2.010eV)......................PL,ZPL
617.00(2.009eV)  G&G[W1995]   Ib+IaA 
 
514
620.0
 
 
 
 619.75(2.000eV)................PL
619.75(2.000eV).............Br,A
620.00 (GIA... phonon sideband GR1)......R
619.96(2667cm-1)[532.0].............2PHR
(N-V)-
514/532
637.0
x
 
 
636.95(1.946eV)..............Br,PL,ZPL
637.20(1.945eV)....Field....R,Heat
NV Center
637.28(1.945eV).....A,CL,PL,R,Heat,ION
637.9(1.943eV)  Field SYN Ib
 
514/532
659.0
x
 
 
658.30(1.883).............A,PL,ZPL,Ib SYN,R, 
658.30(1.883eV)...Davies........Ib,R
659.31(1.880eV)............PL,Lons
659.87(1.878eV)........PL,CVD,ION
 
514/532
680.0
x
 
 
 680.67(1.821eV)......................A,PL.R

 
 

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.

Figure 5

Figure 6

Figure 7

Raman / Photoluminescence Data

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.
 
 

402.7/405.2nm
 
488nm
 
514nm
 
532nm
 

405nm Source

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.
 
 

E Color Data

H Color Data

K Color Data


 
 
 
 
 

514nm Source

E Color Data
H Color Data
K Color Data
 

532nm Source

E Color Data
H Color Data
K Color Data
 

Gems & Gemology Gubelin Data Comparison And Differences

Conclusions



 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 SAS2000 Spectrophotometer   Questions, Comments, Product Support AD