Coupled translation-rotation eigenstates of in and on the spectroscopically optimized interaction potential: Effects of cage anisotropy on the energy level structure and assignments
We have measured the temperature dependence of the infrared spectra of a hydrogen molecule trapped inside a C 60 cage, H 2 @C 60 , in the temperature range from 6 to 300 K and analyzed the excitation spectrum by using a five-dimensional model of a vibrating rotor in a spherical potential. The electric dipole moment is induced by the translational motion of endohedral H 2 and gives rise to an infrared absorption process where one translational quantum is created or annihilated, N = ±1. Some fundamental transitions, N = 0, are observed as well. The rotation of endohedral H 2 is unhindered but coupled to the translational motion. The isotropic and translation-rotation coupling part of the potential are anharmonic and different in the ground and excited vibrational states of H 2 . The vibrational frequency and the rotational constant of endohedral H 2 are smaller than those of H 2 in the gas phase. The assignment of lines to ortho-and para-H 2 is confirmed by measuring spectra of a para enriched sample of H 2 @C 60 and is consistent with the earlier interpretation of the low temperature infrared spectra [Mamone et al., J. Chem. Phys. 130, 081103 (2009)].
Coupled translation-rotation eigenstates of in and on the spectroscopically optimized interaction potential: Effects of cage anisotropy on the energy level structure and assignments
Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C 60 to form the endohedral supramolecular complex H 2 @C 60 . In this confinement, hydrogen acquires new properties. Its translation motion, within the C 60 cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H 2 . We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H 2 , D 2 and HD incarcerated in C 60 . The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C 60 and the high symmetry of C 60 the problem is almost identical to a vibrating rotor moving in a three-dimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H 2 @C 60 . The same parameters were used to predict H 2 energies inside C 70 . We compare the predicted energies and the low-temperature IR absorption spectra of H 2 @C 70 .
Fourier transform infrared (FTIR) spectra have been successfully applied in microbial identification and classification, which provide an alternate method for identification of Chinese cabbage clubroot. Characterization and comparison of the roots and leaves from Plasmodiophora brassicae infested Chinese cabbages were performed based on FTIR spectroscopy in this study. Our results showed that the FTIR spectroscopy of leaves is in general similar to that of roots from P. brassicae infested Chinese cabbage. However, there was a difference in FTIR spectra between roots and leaves of P. brassicae infested Chinese cabbage. In particular, FTIR spectra revealed that 5 peaks at 3380.49, 3011.70, 2854.01, 1744.79, 1244.22 were specific to roots of P. brassicae infested Chinese cabbage. This study indicated that FTIR spectra may give a new strategy for rapid identification of Chinese cabbage clubroot.
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