Onset of nuclear vaporization in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Au</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>197</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mo>+</mml:mo></mml:mrow><mml:mrow><mml:mn>197</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Au collisions

Multifragmentation has been measured for $^{197}\mathrm{Au}$${+}^{197}$Au collisions at E/A=100, 250, and 400 MeV. The mean fragment multiplicity increases monotonically with the charged particle multiplicity at E/A=100 MeV, but decreases for central collisions with incident energy, consistent with the onset of nuclear vaporization. Molecular dynamics calculations follow some trends but underpredict the observed fragment multiplicities. Including the statistical decay of excited residues improves the agreement for peripheral collisions but worsens it for central collisions.