Knowledge Bank

Laboratory spectra of pure, hydrogen- and helium-broadened phosphine were recorded, near $5\mu m$, using high resolution Fourier transform spectrometer (apodized resolution $0.0054cm-1)$. The lines under study belong mainly to the $\nu 2+\nu 4$ transition. A number of lines pertaining to the neighbouring $2\nu 2$ and $2\nu 4(\perp$ and //) bands were also analyzed. A first series of spectra, of pure phosphine under low pressure ($\sim 0.3Torr$) at 296 and 180 K, was used for vibration-rotation analysis and line strength measurements. A second set, consisting of hydrogen- and helium-broadened spectra (total pressure $\sim 120$ Torr) at temperatures ranging from 170 to 296 K, yielded collisional line widths along with their temperature dependence. The true broadening coefficients and line strenths were directly derived from the measured values of the apparent width and peak transmission of the recorded lines. For this purpose, correction tables were previously built up by convolving the instrument function of the interferometer with a series of synthetic Voigt lines of given strengths and lorentzian widths.