Determination of A0 of CH3Br from its Raman spectrum

A value of A₀ = 5.1800 ± 0.0010 cm^?1 for CH₃Br has been determined from an analysis of the ν₄ Raman band, based both on a direct fit of Q-branch frequencies and on ground state combination differences. The constants ν₄, (Aζ)₄, η₄₄, and A_e = 5.2442 ± 0.0015 cm^?1 were also determined. The equilibrium distance of the H atoms from the figure axis is calculated as 0.32077 ± 0.00005 Å. All the fundamental Raman bands of CH₃Br were observed, and experimental results for the ν₁, ν₂ and ν₅ bands are included.     

The ν5 and ν3 Raman bands of CH2D2

The ν₅ and ν₃ Raman bands of CH₂D₂ have been recorded with a resolution of 0.35 cm^?1. The ν₃ state is well known from infrared studies. Three hundred twenty-nine transitions of the ν₅ band were analyzed, assuming an unperturbed upper state, giving a standard deviation on the fit of the upper-state energies of 0.037 cm^?1, The constants A, B, C, Δ_J, Δ_JK, and Δ_K differed significantly from the ground-state values, and ν₅ was determined as 1331.41 ± 0.05 cm^?1. This work represents the first complete analysis of the fine structure of a rotation-vibrational Raman band for an asymmetric rotor. The ν₅ state could not be analyzed in infrared so this investigation, once more, demonstrates the usefulness of the Raman method.     

Elimination of autofluorescence in fluorescence correlation spectroscopy using the AzaDiOxaTriAngulenium (ADOTA) fluorophore in combination with time-correlated single-photon counting (TCSPC)

Fluorescence correlation spectroscopy (FCS) is a frequently applied technique that allows for the precise and sensitive analysis of molecular diffusion and interactions. However, the potential of FCS for in vitro or ex vivo studies has not been fully realized due in part to artifacts originating from autofluorescence (fluorescence of inherent components and fixative-induced fluorescence). Here, we propose the azadioxatriangulenium (ADOTA) dye as a solution to this problem. The lifetime of the ADOTA probe, about 19.4 ns, is much longer than most components of autofluorescence. Thus, it can be easily separated by time-correlated single-photon counting methods. Here, we demonstrate the suppression of autofluorescence in FCS using ADOTA-labeled hyaluronan macromolecules (HAs) with Rhodamine 123 added to simulate diffusing fluorescent background components. The emission spectrum and decay rate of Rhodamine 123 overlap with the usual sources of autofluorescence, and its diffusion behavior is well known. We show that the contributions from Rhodamine 123 can be eliminated by time gating or by fluorescence lifetime correlation spectroscopy (FLCS). While the pairing of ADOTA and time gating is an effective strategy for the removal of autofluorescence from fluorescence imaging, the loss of photons leads to erroneous concentration values with FCS. On the other hand, FLCS eliminates autofluorescence without such errors. We then show that both time gating and FLCS may be used successfully with ADOTA-labeled HA to detect the presence of hyaluronidase, the overexpression of which has been observed in many types of cancer.     

Counterions Control Whether Self‐Assembly Leads to Formation of Stable and Well‐Defined Unilamellar Nanotubes or Nanoribbons and Nanorods

Self‐assembly of the amphiphilic π‐conjugated carbenium ion ATOTA‐1⁺ in aqueous solution selectively leads to discrete and highly stable nanotubes or nanoribbons and nanorods, depending on the nature of the counterion (Cl^? vs. PF₆^?, respectively). The nanotubes formed by the Cl^? salt illustrate an exceptional example of a structural well‐defined (29±2 nm in outer diameter) unilamellar tubular morphology featuring π‐conjugated functionality and high stability and flexibility, in aqueous solution.     

EPR in LiHoF4 with a far infrared laser

A low-temperature FIR spectrometer was used for measuring EPR of LiHoF₄ in the field range 0–7 T, frequency range 150–1600 GHz. Zero field splittings and g-values for the lowest four energy levels are presented. Two sets of hyperfine lines were observed, corresponding to Δm_N = 0 and Δm_N = ?1, each set with line spacings according to $\text{A}\text{h}\text{= 1.57 GHz}$. The exchange part of the molecular field constant is determined and compared to results from previous experiments.     

Zur Bestimmung von Morphin in w?ssrigen L?sungen

Ohne Zusammenfassung     

Prediction of viscosities of hydrocarbon mixtures

A new model for prediction of the viscosities of hydrocarbons including oil and gas mixtures is presented. The model is based on the principle of corresponding states with methane and decane as reference components. The viscosity of a given component or mixture is determined from the reduced viscosities of the reference components using the molecular weight as an interpolation parameter.

The model has been used for prediction of viscosities of both pure components and mixtures over large pressure ranges and for reduced temperatures above 0.476. The results are in good agreement with the experimental data. The new model compares favorably with earlier published methods, which use only one reference component.

Finally, the model has been tested on data for 6 oil mixtures from the North Sea. The mean deviation based on 34 experimental points was 6.4 %.     

The ν2 + ν4 and 2ν2 isotropic Raman bands of 12CH4

The purely isotropic Raman spectrum of the ν₁ band, the ν₂ + ν₄ band (enhanced through interaction with ν₁), and the 2ν₂ band of ¹²CH₄ was obtained with a spectral resolution of 0.30–0.35 cm^?1 from exposures with different orientations of the linearly polarized exciting light. The ν₂ + ν₄ and 2ν₂ bands show partially resolved rotational structure. The spectra are interpreted in terms of a model which takes explicitly into account vibrational and rovibrational interactions with other vibrational states, using molecular constants determined primarily from infrared spectra. The computed contours are in excellent agreement with the experimental ones and the observed and calculated peak wavenumbers agree within one tenth of the spectral resolution limit, except for a small region near the ν₁ band. The good overall agreement represents an independent check on the overall correctness of the previously reported molecular constants. A detailed discussion is given of the contributions to the intensities of individual transitions from the three transition moment matrix elements, which in an isolated-band model are the intensity parameters of the ν₁, 2ν₄, and 2ν₂ isotropic bands, respectively.     

Biphenyltetrols and Dibenzofuranones from Oxidative Coupling of Resorcinols with 4-Alkylpyrocatechols: New Ciues to the Mechanism of Insect Cuticle Sclerotization

Oxidation of 4-alkylpyrocatechols 2 by means of an insect diphenoloxidase (laccase) or K₃ [Fe(CN)₆] yields, in the presence of resorcinols 1 (R² ? H), complex mixtures of products from which biphenyltetrols 3 (R³ ? H) and dibenzofuranones 5 and 6 were isolated. It is suggested that similar homo-coupling products are formed from pyrocatechols 2b and 2c in insects during cuticle sclerotization.