  The so called "isobar run" or RHIC was designed to compare a number of
observables for collisions of $^{96}_{40}Zr$ with those of $^{96}_{44}Ru$,
aimed at identification of $Z$-dependent effects. However, as the STAR data
have shown with unprecedented accuracy, these two nuclides differ stronger than
expected, producing effects larger than those depending on charge. So far,
multiple studies tried to quantify their shape differences, in relation to
various observables. General consensus is that these differences somehow should
be related to nuclear structure, in particularly properties of the lowest
excited states. Yet the precise connection between these fields -- low and high
energy nuclear physics -- is still missing. In this paper I propose such a
connection, via a concept of thermal density matrices of a "preheated" nuclei.
The effective temperature should parameterize which set of excited states
should be included in the calculations. I also suggest semiclassical "flucton"
method at finite temperatures to be used to calculate thermal density matrices.
