Megamaser be very different from those that produce galactic water masers. Observations of water megamasers have been used to make accurate measurements of distances to galaxies in order to provide constraints on the Hubble constant. The word maser derives from the acronym MASER, which stands for "Microwave Amplification by Stimulated Emission of Radiation". The maser is a predecessor to lasers, which operate at optical wavelengths, and is named by the replacement of "microwave" with "light". Given a system of atoms or molecules, each with different energy states, an atom or molecule may absorb a photon and move to a higher energy
Neutron stimulated emission computed tomography sample with neutrons, the measured number of emitted gamma rays of energy characteristic to the nucleus of interest is directly proportional to the number of such nuclei along the incident neutron beam trajectory. After repeating the measurement for neutron beam incidence at positions around the sample, an image of the distribution of the nuclei in the sample can be reconstructed as done in tomography. Neutron stimulated emission computed tomography Neutron stimulated emission computed tomography (NSECT) uses induced gamma emission through neutron inelastic scattering to generate images of the spatial distribution of elements in a sample. NSECT has been shown to