~~Normal-coordinate calculations were performed for the all-truns, 7-cis, 9-cis, 13-cis, 15-cis, 9, 13-di-cis, 9,13'-di-cis, 9,15-di-cis and 13,15-di-cis isomers of p-carotene. The Raman and infrared bands of the all-trans and 1 5 4 s isomers in the solid state were assigned on the basis of the results of the normal-coordinate calculations. The Raman excitation profiles of the main Raman bands of the above two isomers in cyclohexane solution reported previously were satisfactorily correlated with the calculated vibrational modes and the molecular structures in the excited electronic states. The Raman bands of the 7-cis, 9-cis, l3-cis, 9,13-di-cis, 9,13'-di-cis, 9,15-di-cis and 13,15-di-cis isomers were assigned. The vibrational modes assigned to the Raman bands characteristic of the cis isomers were analysed in detail.In the preceding paper' we discussed various aspects of the Raman spectra of the all-trans and 15-cis isomers of P,P-carotene (abbreviated to f3-carotene) from an experimental point of view. It was shown that for both the all-trans and 15-cis isomers (hereafter called simply all-trans and 15-cis), a few types of excitation profile exist in the resonance enhancement of the Raman intensities. In addition to the Raman bands which are resonant with strong absorptions in the visible region, there are some others which are resonant primarily with absorptions in the ultraviolet or near-ultraviolet region. It has also been found that some Raman bands of 15-cis are characteristic of this isomer (and therefore can be used as the key bands for identification) and that there are many weak bands in the Raman spectra of both all-trans and 15-cis in the solid state, which are not clearly observed in the spectra obtained from solutions.The purpose of this study was to establish the assignments of the Raman (and infrared) bands of all-rrans and 1 5 4 on the basis of normal-coordinate calculations and, at the same time, to clarify the relationship between the vibrational modes and the types of excitation profile. The assignments of the main Raman bands of other isomers, namely, 7-cis, 9 4 3 , 13-cis, 9,13-dicis, 9,13'-di-cis, 9,15-di-cis and 13,15-di-cis, which have been reported by Koyama and c o -w o r k e r~,~~~ will also be discussed. METHODring at both ends of the p-carotene molecule was replaced by the simplified structure, The vibrations of the C1-C4 part of the p-ionone ring were assumed not to mix with the vibrations of the conjugated chain which are undoubtedly responsible for most of the bands in the resonance Raman spectra. This assumption was supported by the similarity between the resonance Raman spectrum of all-trans-p-carotene and those of bixin and lycopene which have no p-ionone ring.For all-trans the values of the bond lengths and bond angles determined by x-ray analysis4 were used (Fig. 2a). The planarity of the conjugated chain between Cg and Cg' was assumed, although a slight deviation from a plane was indicated in the result of x-ray analysis. The equality of the C=C-H and C-C-H angles around ...

The phase structure of isotactic polypropylenes isothermally crystallized from the melt has been examined at different temperatures by solid-state high-resolution 13C NMR spectroscopy using VT/MAS (variable temperature/magic angle spinning). On the basis of 13C spin-lattice relaxation and computer line-shape analyses, it has been found that polypropylene samples are composed of not only crystalline and amorphous components but also another noncrystalline component with 31-helical conformation. Similar NMR analyses at different temperatures have revealed that a reversible structural change between the 31-helical and random conformations occurs in the noncrystalline region at 60-110 "C.

Normal-coordinate calculations have been performed for the all-truns, 9-cis, 1 1 4 s and 1 3 4 s isomers of retinal using a model structure in which the p-ionone ring was replaced with a simplified structure. Most of the Raman and infrared bands observed from these isomers in the solid state are assigned on the basis of the results of calculation. The vibrational characteristics of each isomer are discussed.

The Raman spectra (5800–40 cm−1) of the all‐trans and 15‐cis isomers of β‐carotene were observed in the solid state at 77 K and in cyclohexane solutions using laser lines of various wavelengths for excitation. The Raman spectra of the solid samples exhibited not only the well known strong bands but also a great number of sharp bands (mostly weak in intensity) which could not be observed or were observed broadly in solutions at room temperature. The molecules of both isomers in solution seem to have structures slightly different (‘relaxed’) from those in the solid state. All the bands in the region of 5800–1800 cm−1 were satisfactorily accounted for as overtones or combination tones of relatively strong fundamentals. Rough excitation profiles and depolarization degrees measured for cyclohexane solutions gave information on the mechanism of resonance enhancement. The polarized bands of the all‐trans isomer at 1597 and 1525 cm−1 are both resonant with the 1Bu←1Ag absorption around 480 nm. In addition, the 1597 cm−1 band is resonant with the 21Bu←1Ag absorption around 275 nm. The polarized bands at 1597, 1533, 1194, 1156 and 1004 cm−1 of the 15‐cis isomer are resonant with the ‘cis‐peak’ around 340 nm as well as with the 1B1←1A1 absorption around 475 nm. The polarized bands at 1241, 1052 and 953 cm−1 of the 15‐cis isomer are characteristic of this isomer, but these are only slightly resonant with the ‘cis‐peak’. The intensity of the depolarized band at 1564 cm−1 of the 15‐cis isomer is enhanced by the vibronic interaction between the excited 1A 1+ and 1B1 states.