Lower Wavenumber Side Research Articles

Photoconduction in Copper Oxinate

The photocurrent transient in copper oxinate was measured. Copper oxinate has two photoconductive regions: one of them corresponds to the lowest singlet optical absorption band and the other lies in the low wavenumber side of the same band. Under irradiation, the photocurrent in both wavenumber regions abruptly rises to a maximum, and then it decreases gradually and settles to the steady state. In mixed single crystal (69 mol % palladium oxinate–31 mol % copper oxinate), such decreasing of photocurrent is also observed in photocurrent due to copper oxinate, while it is not observed in photocurrent due to palladium oxinate. The decreasing of photocurrent is not caused by the presence of carriers but caused by the excitation of specific molecule (copper oxinate) in the crystal, and the photoconduction in low wavenumber region is attributed to the excitation of copper oxinate.

Hyperfine Structure and Isotope Shift of 30-Year ^207Bi in the 3067-Å Resonance Line*

A 10-m focal length Czerny–Turner monochromator was used to photograph the emission spectrum of 30-year 207Bi in the 3067-A transition to obtain the hyperfine spectrum and the isotope shift with respect to the naturally occurring isotope 209Bi. A procedure was developed for making a low-impurity electrodeless spectral lamp utilizing only nanogram quantities of 207Bi. The radioisotope was produced in a cyclotron bombardment of natural lead, followed by mass separation. Because the nuclear spin, I, of 207Bi is at present unmeasured, the calculated values for the 207Bi magnetic-dipole and electric-quadrupole constants A and B, respectively, and the isotope shift are based on I=92, which is expected on the basis of the nuclear-shell model. The results are ​207Bi A(6p27s⁴P12)=163.8±0.5mKA(6p3⁴S32°)=−14.87±0.06mKB(6p3⁴S32°)=−13.3±5.0mK​207Bi−​209Bi isotope shift=27.3±5.0mK,with the center of gravity of 207Bi on the lower-wavenumber side.

Donor-acceptor complexes formed by perfluoro-organo bromides and iodides with nitrogenous and other bases. II. Band shapes and widths in the absorption spectrum of gaseous CF3I-N(CH3)3

The absorption band centred at c. 77 cm-1 in gaseous mixtures of CF3I and N(CH3)3 previously reported and attributed to the N-I stretching mode of the complex CF3I-N(CH3)3 has been carefully re-examined. This band is of interest as an example of a low frequency ?dissociative type? vibrational mode of a weak molecular complex. The band is asymmetric and apparently structureless with a half intensity width at room temperature of 28-30 cm-1. The width of the band may be accounted for as arising from transitions vi + vi+1 where vi is the vibrational quantum number of the N-I stretching mode with vi up to c. 10 making appreciable contribution to the intensity on the low wave-number side. Centrifugal distortion in the complex is considered. Centrifugal stretching and consequent weakening of the bond may shift the band envelope 2-3 cm-1 to lower wave numbers. Assessment of these and other factors affecting the band shape suggest that the fundamental frequency is probably c. 90 cm-1. The band shape of the vibrational mode of the complex at c. 272 cm-1 is briefly discussed. Many of the considerations presented in this paper should apply to vibration-rotation band shapes in other weak molecular complexes. Some general consequences of anharmonicity for the interpretation of the spectra of weak molecular complexes are discussed.

Vibrational spectra and structure of small ring compounds silacycolpentane

The infrared spectra of silacyclopentane and 1,1-dideutero-1-silacyclopentane in both the gaseous and liquid states were recorded from 4000 to 33 cm −1. The Raman spectra of the liquids were also recorded and depolarization values were determined. The data rule out the planar configurati tn for the silacyclopentane molecules and were shown to be consistent with a C 2 structure. The 39 normal vibrations were assigned on the basis of their depolarization values, infrared band contours, isotopic shifts, and band intensities. The two low-frequency ring modes were observed at 264 and 101 cm −1 for the normal compound, and at 259 and 94 cm −1 for the deuterated molecule. A series of pronounced Q-branches with approximately 2 cm −1 spacing were observed on the low wave-number side of the 101 cm −1 band. A similar series with an approximate spacing of 1.7 cm −1 was observed for the deuterium compound. These series have been interpreted in terms of a relatively high barrier to pseudorotation of the five-membered ring. The calculated barriers were 3.9 and 4.2 kcal/mole for the “light” and “heavy” compounds, respectively. The spectroscopically derived parameter mq 0 2 was 14.2 × 10 −40 and 17.9 × 10 −40 g cm 2 for SiC 4H 10 and SiC 4H 8D 2, respectively. The barriers are considerably higher than one might expect from existing theories and data on torsional barriers.

Infrared-Absorption Spectra of LiOH and LiOD

Spectra of films of LiOH and LiOD in the region from 450 cm—1 (22 μ) to 4500 cm—1 (2.2 μ) are presented. Polarized spectra of crystals of LiOH, LiOD, and mixed crystals of LiOH and LiOD at room temperature and at 15°K are also presented. The OH— ion stretching fundamental at 3678 cm—1 (2.7 μ) and the OD— ion stretching fundamental at 2713 cm—1 (3.69 μ) are each bracketed by sidebands in a nearly symmetric manner. The sidebands on the low wave-number side of each fundamental, the difference sidebands, all vanish at 15°K, while the main features of the sidebands on the high wave-number side of each fundamental, the summation sidebands, are preserved at low temperatures. In addition, the increased resolution resulting from reduced bandwidths at low temperatures reveals several new summation sidebands not observed in the room-temperature spectrum. A correlation of the LiOH and LiOD summation sidebands is presented and the deuteration effects discussed. These effects are observed to be in very good agreement with the theory which assumes that the sidebands are the result of binary combinations of low-frequency lattice modes with those modes which involve the hydroxyl ion stretching motions. They are not, however, in agreement with the rotation theory which proposes that the sidebands of LiOH, Mg(OH)2, and Ca(OH)2 are the results of the coupling of localized rotations of the OH— ions with their internal stretching frequency. An analysis of the mixed-crystal spectra reveals the significant role of hydroxide—hydroxide interactions in producing the observed intensities of the sidebands.