Excitation of carbon monoxide molecules has been carried out in a cold cell and in a low-pressure plasma jet using an ArF
narrow-band excimer laser. The different excitation models are discussed and the relevance of atomic carbon absorption into
the laser cavities is pointed out. Excitation spectra of Cameron bands have been obtained in a room-temperature cell and compared
with calculated spectra. A value of the constant σ related to the interaction strength between a3Π(v = 2) state and its neighbouring singlet states is derived: 0≤σ≤0.05. The fluorescence spectrum following broad band excitation of CO has been observed both in UV and visible. Similar experiments
carried out in a high enthalpy flow have allowed to point out the presence of a3Π metastable carbon monoxide. A method for relative measurements of this species concentration is proposed.
Received 9 April 2001 and Received in final form 13 June 2001 相似文献
Characteristics of the Stark broadened and overlapping 447.1 nm He I spectral line and its forbidden 447.0 nm components have
been measured at electron densities between 4.4×1022 m-3 and 8.2×1022 m-3 and electron temperatures between 18 000 K and 33 000 K in plasmas created in five various discharge conditions using the
low pressure pulsed arc as an optically thin plasma source operated in helium-nitrogen-oxygen gas mixture. Good agreement
was found among our measured line characteristics and their existing calculated values, based on the quasistatic approximation.
Possible influence of the singly ionized oxygen impurity atoms (O II) on the intensity values of the dip between allowed and
forbidden components was found that can explain the disagreement among some existing experimental and calculated line characteristics
data, at higher electron temperatures and densities. On the basis of the observed asymmetry of the 447.1 nm spectral line
profile we have obtained the ion contribution parameter at 1022 m-3 electron density and 8 000 K electron temperature.
Received 20 February 2001 and Received in final form 25 April 2001 相似文献
Using a new experimental setup we have measured UV (hν = 6.4 eV) photoelectron spectra of cold silicon cluster anions Sin- in a very broad size range. For sizes up to n = 46 the spectra exhibit rich structures. For larger sizes only smooth spectra have been obtained. No trace of a bandgap has been
found even for clusters with more than 1000 atoms.
Received 30 November 2000 相似文献
An inversion method for ion Doppler shift of spectrum lines was developed for plasma velocity measurements. By reducing the
problem to the vectorial Radon transform, the characteristics of plasma ion velocity distribution such as vector potential/vorticity
and velocity components were computed in two-dimensional space. Computer simulation of the reconstruction of different vector
potential (vector field) models gives evidence that the reconstruction errors are acceptable, and the method can surely be
used for real experimental data.
Received 10 March 2001 and Received in final form 25 July 2001 相似文献
The main objective of this work is to obtain the electron temperature in an argon surface-wave-produced plasma column at intermediate
gas pressures. After proving that argon upper excited states remain in Excitation Saturation Balance, the value of electron
temperature along the plasma column has been obtained using a modified Saha equation and a corrected Boltzmann-plot. Moreover,
the electron energy distribution function has been verified to be nearly Maxwellian in a 0.8-2.8 torr intermediate pressure
range.
Received 24 July 2000 and Received in final form 19 January 2001 相似文献
Microcystins, hepatotoxic cyclic heptapeptides, are produced by freshwater cyanobacteria, and are classified four groups according to the amino acid structure at unit 7. Normal microcystins contain N-methyldehydroalanine (Mdha) or dehydroalanine (Dha) at unit 7, and command the great part of all microcystins. As unusual microcystin classes, [Dhb7]microcystins, [
- and
-Ala7, or N-MeAla7]microcystins and [
-Ser7]microcystins have been found.
On tumor initiation and/or promotion activities of microcystins, the tumor promotion activity of normal microcystins has been found, but cancer-related activities of microcystins belonging in the other classes have not been clear.
To determine normal microcystins as hepatotoxic tumor promoters, a selective determination method was developed. Only Mdha or Dha in normal microcystins was reacted with glutathione (GSH). The GSH-normal microcystins conjugates were reacted with trinitrobenzene sulfonate (TNBS). The TNB–GSH-normal microcystin conjugate can be determined as the total normal microcystin by colorimetry. After methanolysis of the conjugate, dimethyl TNB–glutamate from the conjugate was determined by liquid chromatography/ultraviolet detection (LC/UV) and/or liquid chromatography/mass spectrometry (LC/MS). The detection limits of the total normal microcystin by colorimetry, LC/UV and/or LC/MS were 1 μg, 10 and 0.1 ng, respectively. 相似文献