CDG Research Methods & Evidence-Based Practice 2 — Questions and Answers
Question 1: Which spectroscopic technique is primarily used to detect the 415 nm absorption line characteristic of Cape series diamonds?
- UV-Vis absorption spectroscopy (Correct answer)
- Raman spectroscopy
- FTIR spectroscopy
- Photoluminescence spectroscopy
Correct answer: UV-Vis absorption spectroscopy
UV-Vis absorption spectroscopy detects the N3 defect center responsible for the 415 nm absorption line that defines the Cape series.
Question 2: FTIR spectroscopy is most valuable in diamond research for identifying:
- Surface polish quality
- Nitrogen aggregation states (Type Ia, Ib, IIa, IIb) (Correct answer)
- Carat weight discrepancies
- Fluorescence intensity levels
Correct answer: Nitrogen aggregation states (Type Ia, Ib, IIa, IIb)
FTIR spectroscopy reveals the infrared absorption patterns of nitrogen defects, allowing researchers to classify diamond types and detect treatments.
Question 3: Raman spectroscopy confirms diamond identity by detecting a characteristic first-order phonon peak at approximately:
- 1000 cm⁻¹
- 1332 cm⁻¹ (Correct answer)
- 1580 cm⁻¹
- 2200 cm⁻¹
Correct answer: 1332 cm⁻¹
The sp³-bonded carbon lattice of diamond produces a sharp, characteristic Raman peak at 1332 cm⁻¹, distinguishing it from graphite or simulants.
Question 4: In photoluminescence (PL) spectroscopy research, the H3 center in diamond is associated with:
- Hydrogen inclusions in untreated stones
- A vacancy-nitrogen complex produced by irradiation and annealing (Correct answer)
- Helium bubbles from natural radioactivity
- High-pressure hydrogen treatment evidence
Correct answer: A vacancy-nitrogen complex produced by irradiation and annealing
The H3 center (vacancy + two nitrogen atoms) is a key PL feature created when irradiated diamonds are subsequently annealed, signaling treatment.
Question 5: The DiamondView instrument aids researchers in distinguishing natural from synthetic diamonds primarily by:
- Measuring refractive index to six decimal places
- Imaging fluorescence and phosphorescence patterns under short-wave UV to reveal growth structure (Correct answer)
- Weighing diamonds to microgram precision
- Mapping surface finish quality with white-light interferometry
Correct answer: Imaging fluorescence and phosphorescence patterns under short-wave UV to reveal growth structure
DiamondView uses intense short-wave UV to reveal growth patterns—such as CVD columnar banding or HPHT cuboctahedral sectors—invisible under standard gemological examination.
Question 6: The silicon-vacancy (SiV) center at approximately 737 nm in photoluminescence spectroscopy is a key research marker for:
- Natural diamonds with silicon-rich inclusions
- CVD synthetic diamonds (Correct answer)
- HPHT-treated Type IIa naturals
- Fracture-filled diamonds
Correct answer: CVD synthetic diamonds
Silicon contamination from quartz reactor components during CVD growth produces the SiV center at 737 nm, making it a diagnostic signature for CVD synthetics.
Question 7: In research methodology for diamond origin determination, which approach provides the most conclusive evidence?
- A single UV fluorescence observation under standard long-wave UV
- Convergence of multiple independent spectroscopic and analytical techniques (Correct answer)
- Visual examination under 60× magnification alone
- Country-of-origin documentation from the seller
Correct answer: Convergence of multiple independent spectroscopic and analytical techniques
Convergent evidence from techniques such as FTIR, PL spectroscopy, UV imaging, and DiamondView provides the strongest, most defensible basis for origin determination.
CDG Research Methods & Evidence-Based Practice 2
Which spectroscopic technique is primarily used to detect the 415 nm absorption line characteristic of Cape series diamonds?