Detector Bandpass Research Articles

用于反光电子谱可调带宽的紫外光子探测器

This paper presents a novel Vacuum Ultraviolet (VUV) bandpass photon-counting detector which was designed to count photons with energies approximately 9.70 eV for inverse photoemission spectroscopy experiments. The performance was analyzed to improve the signal-to-noise ratio and resolution of the spectrum. The geometric structure of this detector is similar to a special Geiger-Muller tube. It is filled with a dilute mixture of acetone vapor and argon gas. The proportion was investigated and ascertained to be close to 1 to 20. A SrF2 crystal was used as the input window to cut off high-energy photons with energies greater than 9.7 eV. Acetone vapor was selected as the functional gas to capture photons. Moreover, it can prevent low energy photons from being detected. The optical bandpass width is less than 100 meV and can be tuned continuously by cooling the SrF2 window. The temperature is controlled by a self-developed cryogenic system with accuracy of ±0.2 K. The relationship between the detector bandpass width and the SrF2 window temperature is calibrated using a deuterium lamp and a grating monochromator. ©, 2015, Chinese Optical Society. All right reserved.

Optimal operating conditions and characteristics of acetone∕CaF2 detector for inverse photoemission spectroscopy

Performance and characteristics of a band-pass photon detector using acetone gas and CaF2 window (acetone∕CaF2) have been studied and compared with an ethanol∕MgF2 detector. The optimal operating conditions are found to be 4mbar acetone pressure and 745±20V anode voltage. The count rate obtained by us is about a factor of 3 higher than what has been reported earlier for the acetone detector. Unlike other gas filled detectors, this detector works in the proportional region with very small dead time (4μs). A detector bandpass of 0.48±0.01eV full width at half maximum is obtained.

Photon detection with n-propanol and C2H6O isomers

We demonstrate that a Geiger–Müller-type bandpass photon detector, suitable for inverse photoemission experiments, can be constructed from a MgF2 entrance window that has a high-energy transmission threshold of 10.97 eV, and ethanol, a detection gas with an ionization potential of 10.48 eV. The photon detector has a mean detection energy of ℏωd=(10.89±0.07) eV and a bandpass of Δℏωd=(0.37±0.05) eV. A photon detector can also be constructed from n-propanol/MgF2 with a mean detection energy of ℏωd=(10.76±0.07) eV and a bandpass Δℏωd=(0.41±0.05) eV. These two new detection gas/window combinations have a higher detection energy and a narrower bandpass than the dimethylether/MgF2 detector [Δℏωd=(0.71±0.04) eV and ℏωd=10.60 eV]. Since all three detectors utilize a MgF2 entrance window, the photon bandpass can be changed straightforwardly by changing the detection gas. For systems that can be easily damaged by electron beams, having the freedom to open up the detector bandpass is an advantage because it can reduce the total electron exposure time.

Comparison of ampholytes used for slab gel and capillary isoelectric focusing of recombinant tissue-type plasminogen activator glycoforms

Four commercial ampholytes: Ampholine and Pharmalyte (Pharmacia Biotech), Bio-Lyte (Bio-Rad) and Servalyt (Serva) were evaluated for their ability to resolve recombinant tissue-type plasminogen activator (rt-PA) glycoforms by isoelectric focusing (IEF) and capillary IEF (cIEF). Each brand of ampholytes focused rt-PA into 3–4 major and 5–6 minor bands on slab gel electrophoresis. Visually, focused bands stained with Coomassie Blue appeared to be similarly resolved by all the ampholytes except for Ampholines, where the bands were closely grouped and more intensely stained. When cIEF was performed, Pharmalytes and Ampholines resolved rt-PA glycoforms consistent with the slab gels. No discernible peaks were detected during cIEF of rt-PA using Servalyts or Bio-Lytes. UV spectrophotometric scans of the components used for cIEF showed that Servalyts absorbed intensely over a range which overlapped the detector bandpass. Bio-Lytes showed absorption over a narrower UV range but still overlapped the detector bandpass, thus preventing the discernment of protein peaks. For this cIEF system the best ampholytes were Ampholines and Pharmalytes.

Correction of Baseline Irregularities in the Gradient Elution of Phytoplankton Pigments by HPLC Using Methanol/Water/Ethyl Acetate

A practical solution is found for an unexplained baseline irregularity occurring during the HPLC analysis of pigments extracted from phytoplankton. Pigments are eluted with 90% methanol/9.4% water/0.6% ethyl acetate for 10 min followed by the addition of ethyl acetate at the rate of 3%/min for 20 min. For two different spectrophotometric detectors, the initial addition of 0.6% ethyl acetate to the mobile phase is necessary to prevent an apparent absorbance change of up to 0.2 AUFS during gradient elution. This irregularity, which does not occur for another detector used, appears to be independent of solvent refractive index, detector bandpass, and transient mixing phenomena. Detector flow cell design is suggested as a possible cause.

Rotational energy transfer and LIF temperature measurements

In a previous study, OH molecules in the burnt gases of a CH 4/air flame were excited to a single v′, J′ level using a laser, and the resulting fluorescence spectra were measured. It was found that the electronically excited OH did not rotationally thermalize before radiating, and it was postulated that this could cause significant systematic errors in rotational temperatures deduced from excitation scans. We here report excitation scans showing quantitative agreement with the results of a model based on the independent information from those earlier rotational population distributions. Errors of several hundred degrees can result using a typical detector bandpass configuration.