I am aware that a similar question has been asked by someone else in the past, but in a very general form. Due to the physics interest and technology, in this question I put emphasis on the detail of the physics part and the question becomes very specific.

We know the power of visible-light-laser and the effects it can have on matter: Industry, Medicine, Military, Entertainment and many other applications.

Given the large amount of energy of $\gamma$-photons, one can extrapolate and see the new applications of LASER designed to amplify $\gamma$-light, emitted by nuclear isomers, which might be called “GLASER” (gamma light amplification by stimulated emission of radiation).

The trick is to excite nuclei to a metastable state, to achieve “population inversion” and then stimulate them to decay simultaneously. The excitation can be achieved either by soft neutron bombardment or by synchrotron irradiation, in order to excite the nuclei into an angular momentum state that does not match the one of the ground state. These nuclei can remain at that state for sufficiently long time, so population inversion can be achieved.


How can the nuclei be stimulated to decay and emit their $\gamma$-photon so that to achieve GLASER? This could depend on how the nuclei are excited in their isomeric states to begin with.

  • $\begingroup$ Again, the intensity requirements for the pump are considerable: the cross-sections for nuclear excitation tend to be very small compared to those for atomic excitation, so it is not going to be easy to obtain and sustain a population inversion. $\endgroup$ Mar 5, 2013 at 23:37
  • $\begingroup$ @dmckee Thanks for your comment, appreciated. It is true that echieving population inversion and stimulation are not easy problems. One has to see the problem from a different angle. Various attempts are in progress with the use of Th-229, which has some very interesting properties. $\endgroup$
    – JKL
    Mar 5, 2013 at 23:59

2 Answers 2


For gamma-ray wavelengths a much better alternative are Free Electron Lasers, since their gain medium is the Bestrahlung and synchrotron electron radiation inside the undulators. They also have the benefit of not being constrained to a nuclear energy state, and they can operate on a range of wavelengths


There are a large number of problems, and a large number of proposed solutions for Graser operation. I published a paper on laser photochemical separation of nuclear isomers to get a population inversion in the 1970s with George Baldwin.

He moved onto LASL where he continued Graser work for some time. His reviews are quite informative.

While technically a nuclear isomer the Th-229m does not produce a very high energy photon. It is more like an X-ray and not as interesting or problematic as a high energy state.

  • 2
    $\begingroup$ I'm sure a reference to the paper would be very much appreciated. $\endgroup$ Apr 9, 2013 at 23:36

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