The intensity of radiation stimulated by laser pulses of arbitrary shape is derived up to the fourth order terms. It is shown that there is a linear fourth order mechanism of emission that depends on linear susceptibilities of molecules. This linear mechanism reveals collective, superradiant features. The intensity of laser-driven spontaneous emission (LDSE) is proportional to N$+2$/ for samples smaller than $lambda$+3$/, where $lambda is a wavelength of emitted radiation, and N is the number of molecules. For extended volumes $GRT$GRT $lambda$+3$/, the intensity of LDSE is proportional to N$+4/3$/. Equations of motion describing collective radiation damping are derived.
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