Hans Henrik Andersen

Andersen was born in Frederiksberg, Denmark.

He has made important contributions to various fields of atomic physics and solid state physics, especially in the field of the stopping power of matter for fast charged particles. The accuracy (0.3–0.5%) of his measurements is unsurpassed even today (2006). They were done by measuring the amount of heat deposited in a foil at the temperature of liquid helium (−269 °C).

Together with his collaborators, he succeeded in showing in 1969 that the stopping power for fast alpha particles is more than four times as large as that for protons. Since the atomic number (Z) of alpha particles is exactly twice as big as that of protons, that means that the stopping power is not exactly proportional to Z2, as the simple Bethe formula would have it. That was an additional proof of the existence of the Barkas effect.

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