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One-color time-of-flight mass spectra (mass resolved excitation spectra) for jet-cooled 4dimethylaminobenzonitrile (4-DMABN) and some of its chemical analogs, dimethylaniline (DMA), 3-dimethylaminobenzonitrile (3-DMABN), N, N-dimethyl-4-(trifluoromethyl)aniline (4-CF3-DMA), and 4-(d 6 -dimethylamino)benzonitrile (4-d 6 -DMABN), are presented and analyzed. Near the origin of the SI ,-So transition the low frequency modes can be assigned to motions of the dimethylamino group for this series of mol~cules. The inversion motion of the dimethylamino group and the dimethylamino group torsion about the Cjpso-N bond (the twist coordinate) in SI give rise to the most prominent peaks in this spectrum. The potential parameters for the twist coordinate of 4-DMABN and DMA are quite similar in SI: B = 0.546, V 2 = 175, and V 4 = 525 cm -I for 4-DMABN and B = 0.546, V 2 = 175, and V 4 = 515 cm-I for DMA. The V 2 and V 4 terms are slightly larger for 3-DMABN and 4-CF3-DMA. The inversion motion is also similar for these molecules but is more anharmonic for the para-substituted dimethylanilines, 4-DMABN and 4-CF3-DMA, than for the meta and unsubstituted molecules. A Franck-Condon intensity analysis for the dimethylamino twist in these molecules suggests that this group in 4-DMABN is displaced in the excited state by -30° with respect to its planar orientation in the ground state. In both solutions and monosolvate clusters of 4-DMABN with polar aprotic solvents, a low lying charge transfer (CT) state is identified in addition to the usual1T1T* excited state of the bare molecule. The relation between the bare molecule 4-DMABN twisting displacement upon excitation and the low lying CT state is discussed.

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