  Magnetically trapped neutral atoms can be cooled with the evaporation
technique. This is typically done by using a radiofrequency (rf) field that
adiabatically couples trapped and untrapped internal atomic states for atoms
with kinetic energies above a value set by the field frequency. The rf-field
can also induce nonadiabatic changes of internal atomic spin states (F,M) that
lead to heating and enhanced loss of atoms. In this paper we use wave packet
simulations to show that the evaporation process can induce these nonadiabatic
transitions which change the internal spin state of doubly spin-polarized (2,2)
trapped atoms. We also verify the validity of a multistate Landau-Zener model
in describing the nonadiabatic dynamics. In addition, we calculate exchange
relaxation rate coefficients for collisions between atoms in the (2,M) states
of 23-Na atoms. Large exchange relaxation coefficients for 23-Na as compared to
87-Rb F=2 suggest that evaporative cooling of (2,2) Na will be more difficult
than for the corresponding state of Rb.
