  The kinetic energy distribution of D$^+$ ions resulting from the interaction
of a femtosecond laser pulse with D$_2$ molecules is calculated based on the
rescattering model. From analyzing the molecular dynamics, it is shown that the
recollision time between the ionized electron and the D$_2^+$ ion can be read
from the D$^+$ kinetic energy peaks to attosecond accuracy. We further suggest
that more precise reading of the clock can be achieved by using shorter fs
laser pulses (about 15fs).

Atomic Physics