On Wed, Jan 20, 2016 at 8:57 PM, H Veeder <[email protected]> wrote:
Eric, your precise analysis suggests to me that the conventional picture of > an isomer is lacking. > This is entirely possible. Also, my description might be lacking. All the literature I have read depicts the formation of a nuclear isomer as > resulting from the bombardment of a target nucleus. > This sounds like Coulomb excitation, i.e., one nucleus coming close enough to another nucleus to produce an inelastic collision. Together the scattered particles have less kinetic energy than that of the incident particles, with the remainder going into an excited state for one of the nuclei. Once this has happened, if the excited state lasts long enough, I assume all memory of the collision is lost and you can draw the system boundary around the excited nucleus. I did not intend the earlier description to preclude the possibility of some kind of electromagnetic stimulation coming along and nudging the isomer out of its excited level into a lower one. I'd be interested if someone knows of something like this. The idea was that such a stimulus isn't required to get a transition, which will happen because there is a half-life, unless we're discussing Bob Higgins's extremely long-lived isomers. The description of isomerism above is to be contrasted with NMR, where the nucleus can be in the ground state and you still see radiation emitted as its alignment is altered under the influence of the perturbing electromagnetic pulse. Eric
