Eric, your precise analysis suggests to me that the conventional picture of an isomer is lacking. All the literature I have read depicts the formation of a nuclear isomer as resulting from the bombardment of a target nucleus. In other words the study of nuclear isomers has yet to become part of condensed matter nuclear science - CMNS - where neighboring fields and applied fields do matter.
Harry On Wed, Jan 20, 2016 at 12:56 PM, Eric Walker <[email protected]> wrote: > On Mon, Jan 18, 2016 at 9:47 AM, Bob Cook <[email protected]> wrote: > > I have always considered any excited nuclear state to be a nuclear >> isomer. I do not know what the elevated energy nuclear state which is due >> to spin energy as established during an NMR energy addition would be >> called. I think it fits the general definition of an excited state with a >> lifetime less than 10-9 sec., and, thus, it is not metastable from that >> standpoint. >> > > In the case of a nuclear isomer, the potential energy is held within the > nucleus itself, as a local minimum in energy that is above the global > minimum (along the lines of Bob Higgins's description). The system > boundary can be drawn around the nucleus. I think of nuclei as clumps of > spherical, frictionless neodymium magnets that arrange in various ways, > perhaps with segments rotating in relation to one another. In the case of > an isomer, you have an arrangement that might eventually shift to a more > stable one later on. > > With NMR, you have the perturbation of the alignment of a nucleus with a > magnetic moment in an external magnetic field by an electromagnetic pulse. > In this second case, unlike in the case of the nuclear isomer, the system > boundary can no longer be drawn solely around the nucleus but instead must > include the external fields. I don't think you'd say that the nucleus in > this second case is an "isomer," or that in general it is in an excited > state. > > Eric > >
