A new scheme of K-labeling for torsion–rotation energy levels in low-barrier molecules

Assignment, fit, and theoretical discussion of the ν10 band of acetaldehyde near 509cm−1

“…The acetamide work [24] also led to a relatively simple labeling scheme for torsion-rotation energy levels in the presence of strong DK and Dv t interactions [25]. Although not discussed here, significant labeling difficulties exist also for acetaldehyde [1], particularly in energy regions with irregular J dependences like that near 620 cm À1 in Fig.…”

“…These labeling difficulties make it impossible for the computer program to locate energy levels with a given set of quantum numbers, and they are, in fact, one of the factors preventing us from extending the present fit to J values greater than 15. We are hopeful that the theoretical ideas and algorithms proposed in [25], which deal only with labeling problems in the presence of strong torsion-rotation interaction, can be extended to treat also labeling problems in the presence of the strong vibration-torsion-rotation interactions studied here.…”

Rotational spectroscopy of methylamine up to 2.6 THz

“…Also we have used a new labeling procedure in the program since the previous labeling procedure was based on searching for the dominant component in basis-set composition of eigenvectors and not for all eigenstates above J = 30 it was possible to find such a component. Therefore the labeling scheme based on searching for similarities in basis-set composition in eigenvectors belonging to adjacent J values described by Ilyushin (2004) was used.…”

The effect of deuterium substitution in the amino group on the internal-rotation barrier of acetamide

“…., according to the increasing order of energy. This labeling scheme of the eigenstates may little reflect physical nature of each level, but is simple and unique in most cases, and is thus more versatile than those adopted in [4,6,8,9]. We employed a computer program described in detail in [13].…”

“…Suenram et al [6] reinvestigated acetamide by introducing a new method: Fourier transform microwave spectroscopy (FTMW) and carried out a global analysis using the q-axis method (RAM) [7], where they included all the data reported in [3,5] in addition to their own FT spectra. More recently Ilyushin et al [8,9] further extended the observation not only to pure rotational transitions in the ground vibrational state, but also to those in excited states of CH 3 internal rotation and to torsion (i.e. internal rotation)-rotation transitions, thereby covering the spectral data on the torsional states with the torsional quantum number up to v = 2 and determined both the V 3 and V 6 internal-rotation potential constants.…”