Quantitative Autoradiographie an Halbleiterma Terial mit Phosphor-diffundierten Standards

A suitable standard smaple was developed and tested on the basis of phosphorus for the quantitative autoradiography of elements of interest in semiconductor technology. By the aid of silicon disks with a phosphorus concentration of 6·10¹⁷ atoms·cm^?2 the error of the quantitative autoradiographic method is determined. The relative mean error of the density measurement is at best ±4%; the relative mean error of the determination of phosphorus concentration by use of an error-free standard sample is about ±15%. This method will be extended to other elements by use of this standard sample of phosphorus.     

Ein Mikropenetrometer

Ohne Zusammenfassung     

Polyhalite and its analogous triple salts

Polyhalite (K₂SO₄ · MgSO₄ · 2CaSO₄ · 2H₂O) and analogue triple salts, where Mg²⁺ is substituted by Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺, have been synthesized. The salts were characterized by thermal analysis, Raman spectroscopy and X-ray powder diffraction. Diffraction patterns and Raman spectra resemble those of natural polyhalite, except K₂SO₄ · CuSO₄ · 2CaSO₄ · 2H₂O. The latter corresponds to the mineral leightonite, which is structurally different.     

3Mg(OH)2·MgSO4·8H2O: A Metastable Phase in the System Mg(OH)2‐MgSO4‐H2O

In the course of investigations relating to magnesia oxysulfate cement the basic magnesium salt hydrate 3Mg(OH)₂ · MgSO₄ · 8H₂O (3–1–8 phase) was found as a metastable phase in the system Mg(OH)₂‐MgSO₄‐H₂O at room temperature (the 5–1–2 phase is the stable phase) and was characterized by thermal analysis, Raman spectroscopy, and X‐ray powder diffraction. The complex crystal structure of the 3–1–8 phase was determined from high resolution laboratory X‐ray powder diffraction data [space group C2/c, Z = 4, a = 7.8956(1) Å, b = 9.8302(2) Å, c = 20.1769(2) Å, β = 96.2147(16)°, and V = 1556.84(4) ų]. In the crystal structure of the 3–1–8 phase, parallel double chains of edge‐linked distorted Mg(OH₂)₂(OH)₄ octahedra run along [–110] and [110] direction forming a pattern of crossed rods. Isolated SO₄ tetrahedra and interstitial water molecules separate the stacks of parallel double chains.     

C-14 tracer studies on zeolite catalysis

To elucidate the mechanism of hydrocarbon conversion on zeolite catalysts, small amount of ¹⁴C-labelled substances were added to the regular feed. Catalytic studies on isomerization of m-xylene and n-butene were carried out in a fixed-bed microreactor and the ¹⁴C distribution was determined by Radio-GC and Radio-HPLC.     

Photophysics and photochemistry of tetraanthraporphyrazines; attempts to obtain a new generation of photosensitizers

Linearly benzo-annulated copper porphyrazines, such as octaphenyltetraanthraporphyrazinato-copper and octapentoxytetranaphthoporphyrazinato-copper, with absorption maxima at about 880 nm, were synthesized. These compounds exhibit very low-lying triplets with an energy below the activation energy of singlet oxygen. Therefore they do not generate singlet oxygen. The transient absorption spectra of the T₁—T_x transition were measured. The solvent dependence of the photophysical parameters in the triplet manifold is discussed. On irradiation in the presence of CBr₄, π-cation radicals are formed.     

Femtosecond Two-photon Excited Fluorescence of Melanin*

Fluorescence of synthetic melanin in dimethyl sulfoxide has been excited by two-photon absorption at 800 nm, using 120 fs pulses with photon flux densities > or = 10(27) cm-2 s-1. The shortest main component of the three-exponential decay of fluorescence is 200 +/- 2 ps. The overall spectral shape is red-shifted with respect to the 400 nm excited fluorescence. Two-photon excited melanin fluorescence also has been measured from excised samples of healthy human skin tissue. Because of the selectivity of melanin excitation via resonant two-photon absorption, it is hypothesized that fluorescence excited in this way may yield information on malignant transformation.     

Absorption, luminescence, and Raman spectroscopic properties of thin films of benzo-annelated metal-free porphyrazines

Thin film properties of the set of metal-free linearly benzo-annelated porphyrazines, tetra(tert-butyl)porphyrazine (tBu-TAPH₂), tetra(tert-butyl)phthalocyanine (tBu-PcH₂), tetra(tert-butyl)naphthalocyanine (tBu-NpH₂), and octaphenyltetraanthraporphyrazine (AnH₂) were studied by laser excitation using micro-Raman and -luminescence spectroscopy. With the exception of tBu-TAPH₂ all compounds are characterized by a broad absorption pattern mainly due to excitonic coupling. A strong bathochromic energy shift for the Q-band absorption per annelated benzo-moiety was found in solution as well as in the solid state in going from tBu-TAPH₂ to AnH₂. Films of tBu-TAPH₂, tBu-PcH₂, and tBu-NpH₂ exhibit a single broad featureless luminescence band with a large Stokes shift, which originates from an excitonic state. In addition, tBu-TAPH₂ and tBu-NpH₂ exhibit photoluminescence peaks emerging from monomer-like molecules. These porphyrazines are the only ones known to show two luminescence peaks each. A systematic decrease in luminescence efficiency of thin films is observed and can be attributed to exciton coupling and migration leading to efficient quenching of the radiative decay channels. It also allows for Raman spectroscopic characterization of the thin films and for the case of tBu-NpH₂ in highly concentrated solutions.The different resonance Raman spectra of the compounds can be used as fingerprint for distinguishing the degree of benzo-annelation.