Gamma Spectrometry
Definition
Energy-resolving detection of gamma rays. Each radioisotope emits a characteristic gamma at a known energy, which is how NAA identifies elements.
- Function
- Energy-resolving detection of gamma rays
- Basis
- Each radioisotope emits gamma rays at characteristic energies
- Application
- Element identification in neutron activation analysis
Common questions
Why is gamma spectrometry paired specifically with neutron activation rather than used alone on a sample?+
The sample must first be irradiated with neutrons so its stable isotopes become radioactive and start emitting characteristic gamma rays; the spectrometer then reads those emissions, but without the prior activation step the original elements would not be emitting any gamma signal to detect.
How does gamma spectrometry quantify an element's concentration, not just its presence?+
The intensity, or count rate, of the characteristic gamma peak for an isotope is proportional to how much of that element was present and got activated, so comparing peak intensity against a known standard irradiated the same way gives a quantitative concentration.
Related terms
- BARC Trombay
- Bhabha Atomic Research Centre, Mumbai. Hosts the Dhruva and Apsara-U research reactors that have historically supplied neutron flux for Indian NAA work.
- Half-Life
- The time required for half the radioactive atoms in a sample to decay. Set by the decay constant lambda through t1/2 =...
- HPGe Detector
- A high-purity germanium semiconductor crystal cooled with liquid nitrogen to about 77 kelvin. Resolution at the 1,332 keV gamma line of cobalt-60...
- INAA
- Instrumental Neutron Activation Analysis. The whole sample is irradiated, cooled, and counted directly. No wet chemistry. Non-destructive.
- Neutron Capture (N, Gamma)
- The reaction in which a stable nucleus absorbs a neutron and becomes a radioactive isotope of the same element, emitting a prompt...
- RNAA
- Radiochemical Neutron Activation Analysis. After irradiation, the analyst chemically separates the isotope of interest to remove interfering activity. More sensitive, destructive.
- Thermal Neutron
- A low-energy neutron (around 0.025 eV) that has been slowed by a moderator. The workhorse particle of NAA because slow neutrons are...