When performing gamma spectroscopy, a scintillation detector is used to measure which of the following?

In gamma spectroscopy, a scintillation detector is utilized specifically to measure the energies of photons, particularly gamma rays emitted during radioactive decay. The scintillation detector works by converting the energy of these gamma photons into visible light, which is then detected and quantified. This process allows for the determination of the specific energy levels of the gamma rays, which is crucial for identifying the isotopes present in a radioactive sample.

Understanding the photon energies is central to gamma spectroscopy because each radioactive isotope emits gamma rays with characteristic energies that can be used to identify the isotope. By analyzing the spectrum of detected energies, one can infer not only the presence of different isotopes but also their relative abundances in a sample.

The other options do not relate to the primary function of a scintillation detector in gamma spectroscopy. While decay rates of isotopes can be important in the context of radioactivity, they are not directly measured in this process. Similarly, the mass of radioactive materials and temperature variations wouldn't be addressed through gamma spectroscopy, as the technique is solely focused on analyzing gamma photon energies for identification and characterization purposes.