Knowledge Bank

Spectra with linewidths of $0.04cm-1$ are presented for the $\nu 1+3\nu 3(a)$ and $\nu 1+2\nu 2+\nu 3+4\nu 40(b)$ bands of acetylene in the $12680-12725cm-1$ range. These were obtained with inexpensive commercial laser diode sources scanned thermally and calibrated by a home-built wavemeter. The spectra show many previously unreported resonances and perturbations, but a preliminary analysis gives the following rotational and centrifugal constants: $B(a)=1.151181(81)cm-1B(b)=1.15837(18)cm-1D(a)=1.10(16)\times 10-6cm-1D(b)=-11.33(72)\times 10-6cm-1$ A more detailed treatment of our results including the effects of the resonances will be presented.