Determination of Einstein- A and linewidth dependence on pressure for 3.4-μm DF spectra. I. Absorption measurements for pure DF

Measurement of v=1-0, P-branch 3.4-{μ}m DF absorption spectra is made for a 0.1- to 500-Torr range of pressure. A cw DF laser is used as a light source, and laser intensity transmitted by DF gas is recorded in order to determine the absorption. The laser frequency is tunable over an interval which corresponds to a Doppler width. This permits measurement of the frequency dependence of transmitted light intensity for each line in the spectra, from which determination of absorption at precisely the absorption peak frequency is made. This latter determination permits evaluation of Einstein-A and linewidth νL⁰ dependence on pressure. The results obtained for v=1-0, $P(5)$ through $P(10)$ spectra are (A in sec^-1, νL⁰ in cm^-1 atm^-1): for $P(5)$, A=28±4 and νL⁰=0.46±0.08; $P(6)$, A=34±4 and νL⁰=0.45±0.07; $P(7)$, A=31±4 and νL⁰=0.29±0.05; $P(8)$, A=35±4 and νL⁰=0.24±0.04; $P(9)$, A=31±4 and νL⁰=0.17±0.03; and $P(10)$, A=34±4 and νL⁰=0.13±0.02. These values for A and νL⁰ are in excellent agreement with corresponding theoretical values.