  The coherent radiation spectrum of two-level polar molecules with UV
transition is studied at the multiphoton resonant excitation by a moderately
strong laser field. The spectrum corresponding to harmonic generation and
low-frequency radiation is investigated both analytically and numerically.
Specifically, a mechanism for generation of intense smoothly tunable terahertz
radiation by two-level molecular configurations (with dynamic Stark shifts)
possessing permanent dipole moments, is considered.
