Rachel format nuclear data files

Rachel accepts the standard Gosia data in addition to the measured relative gamma-ray yield data, in the file <tt>rachel_nuclear_data.txt</tt>.

where "branching," "mixing," "lifetime" and the bra and ket notation are fixed formatting symbols and ''band'' is a valid text band name in Rachel.  The "<", ">" and "||" symbols should be delimited by spaces.  Note the "upward" direction for the matrix element (from lower- to higher-numbered state) and the standard units of the appropriate powers of e, b and nuclear magnetons.  The individual entries can be given in any order, for example in the file <pre>rachel_nuclear_data.txt.EXAMPLE</pre>, which comes with the Rachel distribution:

The order of the individual lines is completely arbitrary.  For example, see the example file [[File:Rachelnucleardata.txt]], which should be renamed as above so that rachel.py will find it in the working directory.  The file is re-read each time Gosia is called, so individual lines can be "commented out" before a Gosia fit iteration.  Note that the sixth line contains a matrix element given in the ''decay direction'', whereas Gosia requires it to be in the ''excitation direction''--from lower-numbered state to higher-numbered state.  This phase of this matrix element will be automatically time-reversed before being included in the fit data.