Collisional energy transfer from vibrationally excited polyatomic molecules

Intensities and decay rates of delayed fluorescence initiated by CO2 laser excitation of the triplet-state molecules are used to probe collisional relaxation of vibrationally excited polyatomic molecules. Collisional efficiencies for large polyatomic molecules are found not to exceed the value of 10(-2)-10(-3) even in most favourable case of vibrational energy exchange in collisions between parent molecules. At intermediate levels of excitation (1500-12000 cm(-1)) the average energies <Delta E > transferred per collision with polyatomic molecules increase as < E(vib)>(m), where m greater than or equal to 2, and decrease with increasing numbers of atoms in the excited molecules.