How to determine the permissible values for which solution of the Schrödinger's wave equation exists?

My textbook( [A Textbook of Physical Chemistry, Dr. O.P. Tandon](http://www.bathlabooks.com/admin/pages/Upload/Title/A%20Textbook%20Of%20Physical%20Chemistry%20for%20Competitions-JEE.jpg) ) says that solution of the Schrödinger's wave equation exists only for certain permissible values which are called eigen values.( physically possible ones).


How to determine the permissible solutions of the wave equation? Please explain.


