Knowledge Bank

The visible absorption spectra of C-H vibrational overtones of several small molecules have been obtained with an accuracy of $0.001cm-1$ using photoacoustic techniques. The spectrometer consists of a modified Spectra-Physics 580A CW single mode dye laser, which has been extended to accomodate an intracavity longitudinally resonant photoacoustic cell based on the design of Kritchman et al. This detector design allows observation of extremely weak absorptions in small gas samples. A Pet microcomputer is interfaced to the spectrometer to permit automated data acquisition and control. The overtone spectra of HCN, $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C2H2$, and several isotopically substituted acetylenes will be presented and discussed.