C. K. Jen

Multiple Trapping Sites for Hydrogen Atoms in Rare Gas Matrices

Hydrogen atoms have been stabilized in nonequivalent lattice sites in matrices of the rare gases at liquid helium temperature. Electron spin resonance spectra of H atoms in argon, krypton, and xenon show that at least two trapping sites are involved in each case. In a neon matrix, H atoms have been stabilized in only one site. Attainability of the various trapping sites apparently depends on the initial energy of the H atom, a simple doublet spectrum being obtained when the atoms are deposited from the gas phase, while multiple trapping spectra are obtained when the atoms are produced by photolysis in the solid.The hyperfine coupling contants and the electronic g factors for H atoms trapped in the various matrix sites have been determined. The deviation of the hyperfine coupling constant from the free‐state value is positive in some cases and negative in others. The experimental results are in good agreement with theoretical predictions. A complex multicomponent H atom spectrum was obtained by photolysis ...

Some Heavy Water Rotational Absorption Lines

Three new heavy water rotational absorption lines have been observed in the microwave region. One of these lines and another line previously observed by McAfee have been identified as HDO lines by a study of the variation of their intensities with isotopic molecular concentration. By interpreting their Stark structure, the two HDO lines are assigned as follows: HDO:8−1→80 at 24 884.85 Mc/sec and HDO:6−2→7−6 at 26 880.47 Mc/sec. In addition, results on the Zeeman spectra of the two identified HDO lines are presented.

Low temperature optical spectra of Zn porphin in triphenylene

The low temperature optical absorption spectra of single crystals of triphenylene doped with Zn porphin have been observed in detail. The spectra consisted of sharp lines, many of which were polarized. This is thought to be the first direct observation of polarized sharp line spectra of a porphyrin. Also observed were a number of weak anomalous absorption lines near the 0–0 transition, but at longer wavelengths. Two different site models were proposed to account for the polarization properties of the spectra. The implication of these results in the interpretation of porphyrin spectra are discussed.

Optical spectra of Cu porphin and VO porphin in single crystal triphenylene

Abstract Polarized optical absorption spectra of copper porphin and vanadyl porphin in single crystals of triphenylene have been obtained at room temperature, 77°K and 4.2°K. Luminescence spectra of these samples are also reported. The gross features of the spectra of these two metalloporphins are similar but the spectral lines in vanadyl porphin are much sharper than those in copper porphin, revealing much more satellite structure. It is shown that the central metal can substantially affect metalloporphyrin absorption spectra, contrary to the case of broad band solution spectra. The data is consistent with porphin molecules in substitutional sites of triphenylene and a crystal field reduction of the usual D 4 h metalloporphyrin symmetry to D 2 h .

Low-temperature optical absorption spectra of hematoporphyrins☆

Abstract Low-temperature optical absorption spectra of both free base and metal complexes of hematoporphyrin have been obtained. Vibrational structure, inferred by others from MORD data, is observed here directly in bands III and IV of the free base. Structure is also observed in the β band of the Ni and Pd metallohematoporphyrins. Implications of these results on the presently accepted theory of porphyrin optical spectra are discussed.

An ESR study of vanadyl porphin

Abstract We report the first ESR spectra of the unsubstituted vanadyl porphyrin. The ESR spectra of vanadyl porphin in its magnetically concentrated form, in a tetrahydrofuran solution, in polycrystalline triphenylene, and in single-crystal triphenylene have been obtained. The hyperfine structure which was observed in vanadyl tetraphenylporphin was not seen in vanadyl porphin, indicating increased dipolar interactions. The data is consistent with porphin molecules in substitutional triphenylene sites, a fact which was not apparent from previous optical studies. The observation of the sample dependence of the number of ESR sites remains as an unexplained anomaly.

Optical fluorescence spectra of porphins in organic crystalline hosts

Abstract The low temperature fluorescence spectra of Zn porphin and free base porphin in four different aromatic crystalline hosts have been observed for the first time. These hosts, anthracene, triphenylene, benzophenone and biphenyl, extend the known number of materials useful for spectroscopic studies of porphyrins. In this report the observations of sharp line fluorescence spectra is evidence that the porphin molecules were incorporated into the respective host lattices, and demonstrates the feasibility of using these materials to study porphin spectra. The spectra of porphins in these hosts indicate the presence of multiple sites. A comparison of the spectra in these hosts and in n-octane (reported by other workers) reveals small variations in the vibration frequencies with the different host materials. The variations in the relative intensities of the electronic-vibration transitions, however, are rather large.