Model for gas-laser interaction: application to thermally activated laser-induced chemical vapor deposition

We present a model for the interaction between a laser and gas mixture that can be directly applied to the case of thermally activated laser-induced chemical vapor deposition (LICVD). The model involves the values of specific parameters, particularly gas pressure, laser intensity, detuning frequency, and rotational and vibrational relaxation rates, relevant to absorption, saturation, and heat-transfer processes and their interrelation. We adopt a semiclassical phenomenological approach, considering vibrational energy levels with accompanying rotational energy manifolds and both radiative and nonradiative transition processes. The model is applied to the experimental NH(3) absorption results at the R(6), R(14), and P(20) lines of a cw CO(2) laser in the 10-microm region.