Two-quantum transitions in nuclear isomers

Two quantum emission in nuclei proceeds with such a small probability that it can hardly be detected unless all competing processes are strongly suppressed. Most favourable would be an excited level that can decay only by a 0+-0− transition but, unfortunately, such a case is not yet known. Another possibility for detecting two quantum transitions might be provided by nuclear isomerism. An isomeric single quantum transition of a high multipolarity may be replaced by the emission of two quanta of lower multipolarities. The calculated angular correlation is generally not symmetric about 90°. The total transition probability and the distribution of energy between the two quanta have been evaluated using the single particle model. The experimental possibility of observing two quantum processes is discussed.