Discrete wavelength

The fact that the photons making up atomic spectra have only certain discrete wavelengths implies that they can have only certain discrete energies, because... 

Our synthetic data simulate spectra that are measured at 100 discrete wavelengths. But, we only have 15 spectra in our training set. Thus, before we can perform ILS on our data, we must first condense our training set data to no... 

The simplest IR sensor would consist of a source, a sample interface and a detector. Although quite sensitive, such an arrangement would have no selectivity as any IR absorbing substance would cause an attenuation of the detected radiation. To get the selectivity that is a main driving force behind the application of IR systems, the radiation has to be spectrally analysed. This can be accomplished either by measurement at discrete wavelengths or, for multi-component sensors or samples containing (potentially) interfering substances, by full spectral analysis of the collected radiation. 

As a result of their unique optical and electronic properties, particularly their ability to fluoresce at discrete wavelengths directly proportional to their sizes and material compositions, QDs have found use in many fields, including electronics, biology, medicine, and even cosmetics. The first attempts to modify their surface characteristics to make them water-soluble and biocompatible eventually led to their use as fluorescent labels for biomolecules in many applications (Rogach et al., 1996 Bruchez et al., 1998 Chan and Nie, 1998). 

Fig. 9.1. Emission can be continuous across all wavelengths or at discrete wavelengths (shorter wavelength on right and longer on the left).

IR instruments are available in filter-based, grating-based, and FT-based models. The usual approach is to use a full-spectrum model to ascertain the working wavelengths for a particular reaction, then to apply simpler filter instruments to the process. This works where one, two, or three discrete wavelengths may be used for the analysis. If complex, chemometric models are used, and full-spectrum instruments are needed. 

One, by Macaloney et al.,39 discusses biomass and glycerol in an E. coli K12 fermentation process. MLR was used wherein discrete wavelengths were identified to have relationships with the constituents in the broth. The correlation and SEP for the glycerol were 0.98 and 0.3 g/1, and for the biomass they were 0.99 and 0.2 g/1. 

The pyroelectric DTGS detector is a very useful low-cost, general purpose, wideband NIR detector well suited for use in FT-based analyzers. It is not normally used in scanning monochromators where higher sensitivity detectors are needed to match the lower optical throughput and discrete wavelength scanning requirements. 

The energy separation between the non-degenerate and degenerate states can be assessed by fitting the MCD intensity as a function of 1/T at a discrete wavelength to a Boltzmann population distribution for a two level system. 

Because the actinic flux data are reported as averages over certain wavelength intervals, rather than integrating over Eq. (OO) in a continuous manner, in practice one calculates the sum of the product actinic fluxes are reported as averages over 2-nm intervals from 290 to 320 nm, which is important for the 03 absorption, 5-nm intervals from 320 to 420 nm, 10-nm intervals from 420 to 580 nm, and 20-nm intervals from 580 to 700 nm. Since the primary quantum yield, ( A), and the absorption cross section, a(A), are not normally reported over identical intervals, representative averages of these parameters over the same intervals for which the actinic flux data are reported must be calculated from the literature data. 

Neutron activation (NA). The sample is bombarded with neutrons and the radioactivity induced in the sample is then measured. Both /3 and y radiation can be monitored, but y radiation is more frequently used because of the discrete wavelengths associated with emission that can be used to identify the emitter. 

Figure 2.6 Nodal properties of standing waves. A one-dimensional oscillation (wave) constrained within a space of length L can have amplitudes (wavefunctions) of discrete wavelengths only. The open circles are the nodes where the amplitude is always zero...

Now that we ve seen how atomic structure is described according to the quantum mechanical model, let s return briefly to the subject of atomic line spectra first mentioned in Section 5.3. How does the quantum mechanical model account for the discrete wavelengths of light found in a line spectrum ... 

The tunable filter technology also has distinct PAT advantages. Rapid timing of discrete wavelengths through software control and no moving parts enables the collection of data sets comprising approximately 80 000 spectra in a matter of a couple of minutes. For most... 

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