A general treatment is given of the effects of slit-widths upon emission lines, absorption lines, and continuous absorption spectra. The fundamental approximation is a triangular shaped slit function of base 2seff, where the effective slit-width seff is related to the geometrical slit-width sg as seff2=so2+sg2, so being a function of the frequency characteristic of the individual spectroscope.
A formula is given for the observed shape of an emission line. The observed width L is derived from its ideal width l as L2=l2+seff2. The same formulas are valid for absorption lines for sufficiently small values of the optical density D. For larger D the mathematical difficulties of a general treatment are insuperable, the more so because the superposition principle does not hold. For the maximum point it is shown that neither Beer’s law nor Lambert’s law is experimentally fulfilled in many cases. A correction term is given for the effect on absorption spectra linear in log∊ versus cm−1, where ∊ is the molar extinction coefficient. The possibilities of an experimental determination of the function so are discussed on the basis of the formula L2=l2+sg2+so2.
© 1954 Optical Society of AmericaFull Article | PDF Article
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