Shape coexistence in Hg 190

Levels in $^{190}\mathrm{Hg}$ were studied by radioactive decay of isotopically separated $^{190}\mathrm{Tl}$. A new band was observed with spin parity (energy, keV) of ${0}^{+}$(1279), ${2}^{+}$(1571), ${4}^{+}$(1975), and ${6}^{+}$(2510). Electric monopole transitions were observed between this band and the ground-state band. Relative B(E2) values for intraband transitions in the new band were found to be \ensuremath{\sim}200 times those for interband transitions. Systematics of shape coexistence in the light Hg isotopes and their possible relevance to recent observations of superdeformation in these nuclei are discussed.