  We present an experimental and theoretical study of electron tunnelling
through quantum dots which focusses the attention on the amplitude of the
current peaks as a function of magnetic field. We demonstrate that the
amplitudes of the current peaks in the tunnelling spectra show a dramatically
different behaviour as a function of the magnetic field, depending on the
angular momentum of the dot state through which tunnelling occurs. This is seen
in the non-monotonic behaviour of the current amplitude in magnetic field.
Furthermore, the magnetic field severely hinders tunnelling through states with
angular momentum parallel to the field, and in some cases it makes it
altogether impossible. This type of investigation allows us to directly probe
the details of the confined wave functions of the quantum dot.
