spectra. Between electron and nuclear spins, this is
termed the nuclear HYPERFINE interaction. Between
electron spins, it gives rise to relaxation effects and
splitting of the EPR spectrum.
spin trapping In certain solution reactions, a tran-
sient RADICAL will interact with a DIAMAGNETIC
reagent to form a more persistent radical. The prod-
uct radical accumulates to a concentration where
detection and, frequently, identification are possible
by ELECTRON PARAMAGNETIC RESONANCE SPEC-
TROSCOPY. The key reaction is usually one of attach-
ment; the diamagnetic reagent is said to be a “spin
trap,” and the persistent product radical is then the
“spin adduct.”spontaneous fission Fissioning that occurs without
any outside cause, such as bombardment with a neutron.254 spin trapping
View of a technician using a high-resolution spectrometer in a research laboratory. The instrument is being used to analyze minute sam-
ples of particular chemicals or substances. Spectrometers work by producing a spectrum of light that can vary from X rays to infrared
radiation (spectrophotometers). The effect of a particular substance on a spectrum is analyzed and interpreted by the spectrometer. The
results, displayed graphically on a screen or printout, provide information on chemical composition or molecular organization of the
substance.(Courtesy of Geoff Tompkinson/Science Photo Library)