International Summer School in Nuclear Physics, Predeal, Romania, 28 August - 09 September 2006, pp.112-114
A gamma-rigid version (with gamma = 0) of the X(5) critical point symmetry is constructed. The model, to be called X(3) since it is proved to contain three degrees of freedom, utilizes an infinite well potential, is based on exact separation of variables, and leads to parameter free (up to overall scale factors) predictions for spectra and B(E2) transition rates, which are in good agreement with existing experimental data for Os-172 and Pt-186. An unexpected similarity of the beta(1)-bands of the X(5) nuclei Nd-150 Sm-152 Gd-154, and Dy-156 to the X(3) predictions is observed.