  Since there are quantization ambiguities in constructing the Hamiltonian
constraint operator in isotropic loop quantum cosmology, it is crucial to check
whether the key features of loop quantum cosmology, such as the quantum bounce
and effective scenario, are robust against the ambiguities. In this paper, we
consider a typical quantization ambiguity arising from the quantization of the
field strength of the gravitational connection. An alternative Hamiltonian
constraint operator is constructed, which is shown to have the correct
classical limit by the semiclassical analysis. The effective Hamiltonian
incorporating higher order quantum corrections is also obtained. In the
spatially flat FRW model with a massless scalar field, the classical big bang
is again replaced by a quantum bounce. Moreover, there are still great
possibilities for the expanding universe to recollapse due to the quantum
gravity effect. Thus, these key features are robust against this quantization
ambiguity.
