Knowledge Bank

We have re-examined the $\nu 4$ bands (Herzberg numbering) of $C6H6$ and $C6D6$ using high resolution $(0.0015cm-1)$ Fourier transform infrared spectroscopy. The spectra were taken with the benzene samples in a temperature stabilized cell $(4\circ C)$, 20 cm in length. The $-h6$ sample spectrum $(99.95atom\%\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C6)$ was recorded with an MCT detector and KBr beamsplitter and the $-d6$ sample spectrum was recorded with a silicon bolometer detector and mylar beamsplitter. For the $\nu 4$ band of $C6H6$, we have fit the following preliminary spectroscopic constants: $\nu 0=673.9747(2)cm-1,B\prime =0.1896388(13)cm-1(C\prime \prime -B\prime )-(C\prime \prime B\prime \prime )=0.1897739(10)cm-1,DJ\prime \prime =4.123(45)\times 10-8cm-1,DJK\prime \prime =-6.94(5)\times 10-8cm-1$. For the $\nu 4$ band of $C6D6$, we have fit the following preliminary spectroscopic constants: $\nu 0=496.2086(1)cm-1B\prime =0.156919(5)cm-1$ and $B\prime \prime =0.157016(5)cm-1$. Band centers of the observed sequences of hot bands for both isotopic modifications will be reported.