We study spontaneous emission of electromagnetic radiation by an electron w
ith given initial asymptotic momentum in interaction with a Coulomb field a
nd with a homogeneous monochromatic electric field (laser field in dipole a
pproximation). The intense field effects are taken into consideration for t
he initial and final continuum electron states, by using improved Volkov-Co
ulomb wave functions, including second-order corrections in the interaction
with the electromagnetic field. For the evaluation of the transition ampli
tudes, the so-called three-delta approximation introduced by Korol [A. V. K
orol, J. Phys. B 28, 3873 (1995)] is adopted. The numerical results are pre
sented for a linearly polarized field of frequency of 0.117 eV, intensities
up to 10(-6) a.u., electron energies in the range 50-500 eV, and incident
momentum orthogonal to the laser polarization direction. The study focuses
on spontaneous emission accompanied by exchange of a fixed number n=0, +/-1
,+/-2 of photons with the external field. Deviations from Born results are
shown in several cases. We illustrate in graphs how the spontaneous emissio
n is drastically reduced by the presence of the external field.