Investigation of the spectral characteristics of high-pressure pulsed CO$_2$ lasers

A theoretical analysis is made of some features of the emission spectra of high-pressure CO$_2$ lasers. Dependences of their spectral characteristics on the main parameters of lasers utilizing $^{12}$CO$_2$ and $^{13}$CO$_2$ molecules are determined. It is shown that simultaneous lasing due to several transitions is typically found for pulses of $\lesssim1\mu$sec duration, whereas single-frequency lasing due to the $P(20)$ transition for $^{12}$CO$_2$ and due to the $P(16)$ transition for $^{13}$CO$_2$ may occur for longer pulses.