Morse potential, symmetric Morse potential and bracketed bound-state   energies
  An upgraded concept of solvability of Schr\"{o}dinger-type equations is proposed. In a broader methodical context of non-perturbative quantum theory the innovation involves potentials which are piece-wise analytic yielding differential equations solvable in terms of special functions. In our illustrative example, Whittaker functions are employed and a single point of non-analyticity is admitted in the origin. In a symbolic-manipulation-based practical implementation of the method a serendipitous advantage of the construction of bound states is found in the both-sided nature of the numerical localization of their energies. 
Miloslav Znojil
quant-ph