Sputtering of biomolecules by fast heavy ions

Abstract

We propose a new mechanism that describes the sputtering of biomolecules. A biomolecule is a long chain twisted into a ball shape. The surface atoms of the ball have weakly bound hydrogen with binding energies of I s ∼ 10 −2 eV, whereas the inner atoms have binding energies I in an order of magnitude higher. The electron excitation, caused by fast (> MeV/nucleon) heavy ions, relaxes initially due to electronic heat conductivity of the bulk molecules. But when the electron temperature decreases to T < I in, the inner region of the molecule becomes nonconducting and electron excitation expands only through the surface region of the balls where the electron energy is enough for excitation of weak bonds ( T > I s). This results in heating of the ball surface and the ball is ejected. Most features of biomolecule sputtering can be explained.