Size spectrometer

In the conventional NMR system used in chemical analyses, downsizing of the spectrometer alone may not be appealing, unless other parts of the system, such as a superconducting magnet, a power amplifier, etc., are also miniaturized. On the other hand, the small-sized spectrometer would find interest in various unconventional scenes. In this section, we show examples of such. 

Gel permeation chromatography for small molecules is a relatively recent development in chromatographic techniques. In 1968 Hendrickson ( ) predicted, "It appears likely that GPC for small molecules will become a new basic tool that could be called a liquid phase size spectrometer."... 

Wiedensohler A et al (2012) Particle mobility size spectrometers harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions. Atmos Meas Tech 5 657-685... 

Knollenberg and Huffman (1983), using laser-based size spectrometers, find a large-particle sedimentation mode with modal radius of about 1.8 pm at 15 km and about 1.3 pm at 20 km. This fact is in agreement with the assumption that the amount of H2SO4 in the particles remains relatively constant and that particles at the two heights are characterized by a different dilution. In that case, if particles at 20 km had a 75% H2SO4 concentration, the concentration at 15 km would be around 30%. 

TSI Aerodynamic particle size spectrometer model 3327provides two measurements, aerodynamie diameter and light-scattering intensity, in the size range 0.5 to 20 pm. The generation of paired data makes the instrument of partieular interest to aerosol scientists. 

Unfortunately, any discussion of Raman signal dependence on spectrometer variables is complicated by the many different ways experiments can be performed. Laser spot size, spectrometer slit area, depth of field, and several other variables affect the magnitude of C, and, in some cases, the way it... 

Application of chip-size spectrometers in lab-on-a-chip devices... 

Fig. 4. (a) Setup for chip-size spectrometer calibration, (b) Snapshot of CMOS camera. 

Fig. 7. faj Conceptual cross-section of lab-on-a-chip device with integrated chip-size spectrometer. 

An optical characterization unit based on fluorescence spectroscopy-on-a-chip is described. It comprises a compact fluidic platform that is integrated onto a chip-size spectrometer. The analyte is continuously excited within a novel waveguide. Fluorescence spectra are recorded as the analyte traverse the detection area. 

Compact spectrometers can be integrated along the fluidic channel. The spectrometers are composed of a detector array which is coated with a linear variable band-pass filter. The filter converts the spectral fluorescence information into a spatially dependent signal that is analyzed by the detector array. These chip-size spectrometers are especially applicable for characterization of moving analytes. 

Keywords, spectroscopy-on-a-chip chip-size spectrometer optofluidics. 

We have measured the fluorescence spectram emitted from the anti-resonantly excited Alexa dye in the fluidic channel with a chip-size spectrometer as discussed above and with a conventional spectrometer (see Fig.6). The spectra are normalized to their 633nm intensity in order to ease comparison. Both show a sharp peak at 532nm caused by scattered excitation light and a broad peak around 633nm from the Alexa fluorescence. In... 

As a last feature we will discuss the slight oscillations added to the spectrum measured with the chip-size spectrometer. These are caused by Fabiy-Perot oscillations within the protection layer on top of the CMOS chip in the camera. An appropriate anti-reflection coating on top of the protection layer will efficiently remove this artifact. Moreover, for a real device the protection layer will be replaced by depositing the graded filter directly on top of the CMOS chip. 

A Size-Spectrometer based on an Inertial Impactor. Inertial impactors are devices where an aerosol is accelerated through a nozzle, forming a jet wluch impacts perpendicularly against a collector plate (21) This simple scheme has the remarkable property of acting as a low-pass filter, in which particles smaller than a critical diameter remain in suspension, while those supercritical impact on the surface and are captured. The parameter governing the subcritical-supercritical transition is generally called the Stokes number S ... 

In conclusion, electrospray atomization followed by a DMA and an aerosol size spectrometer provides a scheme suitable for on-line sizing of monodisperse nanoparticles originally in solution. However, one must carefully avoid interferences from residue particles formed in the electrospray. 

Gebhart J, Bol J, Heinze W, Letschert W. A particle-size spectrometer for aerosols utilizing low-angle scattering of the particles in the laser beam. Staub-Reinhalt Luft 1970 30 5-14. 

The fluorescence lines can be resolved with medium sized spectrometers. The demands of experimental equipment are much less stringent than those necessary for complete resolution and analysis of absorption spectra of the same molecule. This advantage still remains if a few upper levels are simultaneously populated under Doppler-limited excitation [8.59]. 

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