Knowledge Bank

A diode laser has been employed to examine the Q branch absorption lines of the $\nu 2$ band for the following $CO2$ isotopes: $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C16O17O, 13C17O2, 13C417O18O$ AND $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C18O2$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C18O2$. An analysis of the relative frequency spacing between the absorption lines yielded the following values for $\Delta B$ expressed in units of $10-3$ $cm-1$: 1.016(2) for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C16O17O,0.964(1)$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C17O2$, 0.9163(3) for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C17O18O$ and 0.891(2) for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C17O2$. Values for $\nu o$, the band origin, were also obtained by super-imposing on the spectra known absorption lines of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O18O$. The following values were obtained for $\nu o:645.7440(2)$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C16O17O,643.0064(1)$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C17O2,640.5680(1)$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C17O18O$ and 638.1149(5) for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C18O2$. The above listed errors for $\nu o$ are associated only with the statistical fitting of the data; the absolute accuracy depends upon the $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}C16O2$ reference lines which are known to about $\pm 0.001$ $cm-1$. A comparison of the diode laser results are made with previous measurements utilizing Fourier transform spectroscopy.