Extraction of energy transfer rate constants from the pulsed laser generated thermal lens spectrometer signal

The details of the short-time (～μ sec) rise of the pulsed source thermal lens signal have been analysed experimentally and theoretically. The effects of a pressure wave, propagated with the velocity of sound, have been demonstrated and shown to be dominant at high pressures (～ 500 torr) in cyclopropane. At lower pressures behaviour governed by the V-T energy transfer constant is clearly exhibited. A reasonable agreement between the rise time then observed and the published fluorescence decay constant is obtained.     

Strain-field investigations with plane diffraction gratings

The development of means for producing small, separate, plane diffraction gratings as integral parts of the surfaces of flat metal specimens has led to modification of the method of Bell and to the investigation of strain fields by study of diffraction phenomena. Choice of a particular diffraction-strain relationship and the use of master gratings in conjunction with diffraction gratings to be used as strain gages permits use of simple optical instrumentation. The diffraction phenomena from multiple gages at the same orientation may be photographed simultaneously during loading for subsequent analysis, and instrumentation in the form employed permits resolving strain increments of magnitude 0.0008 in the range 0.0030 to 0.030.     

Bestimmung einzelner Elemente in organisehen Verbindungen

Ohne Zusammenfassung     

A computer-based spectrophotometric study of the kinetics of the aquation of halogenopentammine-chromium(III) perchlorate

Conventional determinations of rate constants k from absorption spectra employ a few selected wavelengths: by digitizing the complete spectrum computer calculations of k can be made at most wavelengths, and hence with better precision. This has here been satisfactorily tested for the aquation of halogenopentamminechromium(III) perchlorate. Two independent procedures are described, which are approximately equally onerous on computer time. Additionally, these procedures are shown to yield identical computer-generated spectra for the halogeno-complex before aquation commences, and accurate time infinity spectra, of the aquo-complex, for long half-life reactions. They also efficiently eliminate the effects of spectrophotometer instability over long periods of time.     

Gas phase thermal diffusivities by a thermal lens technique

A simplified design of thermal lens apparatus is presented in which a chopped cw argon laser beam produces a transient thermal lens in a cylindrical gas cell. The axial intensity variation of a cw helium-neon laser probing this lens is analysed to yield the thermal diffusivities and thus the thermal conductivity coefficients of Kr, CO₂, CH₄, C₂H₆, C₃H₈, C₃H₆ and C₄H₁₀ as 9.4 × 10^?3 ± 4%, 1.6 × 10^?2 ± 3%, 2.98 × 10^?2 ± 4%, 2.03 × 10^?2 ± 4%, 2.05 × 10^?2 ± 7%, 1.6 × 10^?2 ± 8% and 1.9 × 10^?2 ± 8% respectively in W m^?1 K^?1 at 300 K. The method is rapid, requiring only that the sample be transparent at both laser frequencies used. A simplified mathematical analysis is shown to be adequate for this system. For the conditions specified, self-lensing of the argon laser beam is shown to be compensated by using an effective laser beam diameter.     

Laboratory measurement of absorption by ammonia around 5 microns

Infrared absorption by ammonia has been measured between 2000 and 2200 cm^-1 using samples of the gas diluted by hydrogen, helium and nitrogen. Data on absorption coeffiecients have been obtained employing path lengths up to ten meters and total pressures up to 8 atm. In the three cases of broadening studied, it is apparent that the measured absorption is neither due to the far wings of lines in the bands surrounding the region nor due to any dimer absorption. Thus, the observed absorption should be totally accountable by absorption due to local lines in the region.     

Spectrum of water vapor in the 1.9 and 2.7μ regions

The rotational structure of the ν₁, ν₃, 2ν₂, ν₁ + ν₂, and ν₂ + ν₃ bands of water vapor has been recorded using a high resolution vacuum infrared spectrograph. Values for the energy levels of the ground vibrational state and of the upper states of these bands have been determined. Several intensity anomalies have been observed in lines previously assigned to the ν₁, ν₃, and 2ν₂ bands. Experimental results for these intensity anomalies have been presented.     

The (p, 2p) reaction on 2H, 3He and 4He

The (p, 2p) cross sections on ²H, ³He and ⁴He were measured at 65, 85 and 100 MeV. The experimental data show rather strong energy and target mass dependence, particularly for ⁴He.     

Copper and palladium complexes with N-heterocyclic carbene ligands functionalised with carboxylate groups

The new imidazolium salts functionalised with the trimethylsilyl ester group 1a–c, were easily obtained by quaternisation of alkyl- or aryl-imidazoles with trimethylsilyl bromoacetate. Salt 1a was isolated and fully characterised. It reacted with mesityl copper (Cu₅Mes₅) under trimethylsilyl abstraction to form the complex 2. Methanolysis of 1a–c gave good yields of the carboxylic acid functionalised imidazolium salts 3a–c. Deprotonation of the latter in liquid ammonia led to the zwitterionic imidazolium carboxylates 4a–c. Reaction of 4a with (Cu₅Mes₅) gave solutions from which the insoluble polymeric 5a crystallised slowly. Generation of the carboxylate-functionalised NHC in situ followed by reaction with Pd(OOCCH₃)₂ gave the new complex 6a in which the NHC-carboxylate ligand is chelate bidentate.