Element Fingerprint (IMAGE) Northwestern University Caption Gamma ray spectra resolved by cesium lead bromide (CsPbBr3) detector. The radioactive isotopes used are americium-241 (half-life 432.2 years) and cobalt-57 (half-life 270.9 days). Each isotope possesses its own "fingerprint": a different decay behavior and a unique characteristic gamma-ray emission spectrum. Credit Northwestern University Usage Restrictions Credit must be given License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.