  From the comparison of absolute intensities of the two-step gamma-cascades
and known intensities of their primary and secondary transitions, the cascade
and total population of about ~100 levels of 181Hf and 184,185,187W excited in
thermal neutron capture was determined. These experimental results and
intensities of two-step cascades to the low-lying levels of mentioned nuclei
were reproduced in calculation using level densities with clearly expressed
step-like structure. Radiative strength functions of the primary transitions
following gamma-decay of these compound nuclei to the levels in the region of
pointed structure are considerably enhanced. Moreover, population of levels
below 3 MeV can be reproduced only with accounting for local and rather
considerable increase in radiative strength functions of the secondary
transitions to the levels in vicinities of break points in energy dependence of
level density and significant decrease of that to lower-lying states.
Simultaneous change in both level density and strength functions in the same
excitation region of a nucleus corresponds to the definition of the
second-order phase transition.
