Knowledge Bank

The origin of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}B2-2A1$ transition of $NO21,2$ is assigned to a near-infrared absorption band at 11 $956cm-1$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}NO2$ and 11 $984cm-1$ for $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}NO2$. This band system has an irregular vibrational structure which, together with the anomalously large isotope origin shift, is attributed to vibronic coupling with higher vibrational levels of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A1$ ground state. A krypton ion laser (15 $449cm-1)$ excites four transitions and in a band, $\nu 0=15455.3$ $cm-1$, whose probable assignment is (050) - (000). Resonance fluorescence from the upper state occurs to ground state levels $n1\nu 1+n2\nu 2$ with $n1=0-2$ and $n2=0-5$. Analysis of the fluorescence gives approximate values of the rotational constants $A=6.0$ and $1/2(B+C)=0.345$ $cm-1$ corresponding to red-degraded K- and N-structure. In view of the vibronic coupling these constants are not sufficient to determine the geometrical structure of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}B2$ state.