Knowledge Bank

“(A) HCOF and $DCOF2$ are accidentally nearly symmetric tops having components of the dipole moments along both the least and intermediate axes of inertia. The absorption regions often appear as widely spaccd Q branches superposed on bands with PQR structure. At this time all of the fundamentals have been examined with a grating spectrograph and all except the C-H stretch in DCOF were resolved. A number of overtones and combination bands have also been examined. The analysis of the FCO bend and C-F stretch are complete and the analysis of the planar C-H bending is well begin in both molecules. A slide showing the constants calculated to date will be shown. (B) The fundamental bending vibration, $v2$, of $NO22$ was reinvestigated, and the difference band $2v2-v2$ was recorded for the first time. The band centers and rotational constants were determined for each band from a rotational analysis performed using combination relations. From the band centers, the anharmonic constant. $X22$ was calculated. The line frequencies, rotational constants, and band center found for the $v2$ band were seen to agree very well with previous results, while the value obtained for the anharmonic constant, $X22$ differed substantially from the only previously quoted $value.3$ In 1953, Gordon E. Moore observed nine overtone and combination bands of $NO2$. Using these frequencies, as well as an earlier determination of $v2$ he obtained a complete set of vibrational constants, including $X22=-8.1\pm 3.3$ $cm-1$. The value of $X22$ found in this investigation is $-0.6$ $cm-1$. A new set of vibrational constants was determined using Moore’s data together with present measurements. Calculated frequencies of bands using this new set were found to agree quite as favorably as those computed from Moore’s constants.”