Knowledge Bank

The ultraviolet absorption spectra of ($CH3)4CNH2$ and ($CH3)3$ $CND2$ vapor have been observed in the region of 1900--2430 \AA. There is an electronic band whose 0--0 peaks are observed at 2351 and 2334 \AA, respectively. The absorption band of the deuterated species consists of a few progressions of the amino-wagging vibration, and this structure is explained by assuming that in the $A~$ electronic state the amino group is planar and that its wagging potential is only slightly anharmonic with small positive anharmonicity constant. The observed structure of the band of the undeuterated species indicates that there is a large coupling of the amino wagging and skeletal stretching and /or methyl rocking vibrations. The intensity distribution among the absorption peaks in the observed progressions is explained by taking Franck-Condon integrals into account.