Ultraviolet-visible emission

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

Hahde complexes of Cu with nitrogen base ligands are known to exhibit another form of reversible spectral change known as fluorescence thermochromism. The example of Cu4l4(Py)4 from Table 1 is typical and shows red shifting ia the visible emission spectmm while the sample is both cooled and irradiated with a 364 nm ultraviolet source (7). 

Historically, the visible emission lines shown in Figure 15-3 were the first atomic hydrogen lines discovered. They were found in the spectrum of the sun by W. H. Wollaston in 1802. In 1862, A. J. Angstrom announced that there must be hydrogen in the solar atmosphere. These lines were detected first because of the lesser experimental difficulties in the visible spectral region. They are called the "Balmer series because J. J. Balmer was able to formulate a simple mathematical relation among the frequencies (in It S). The ultraviolet series shown in Figure 15-3 was... 

It is idle to pretend that a definite comparison of optical (ultraviolet, visible, and infrared) emission spectrography with x-ray emission spectrography can be made at this time. We give in Table 8-4, with little qualification and no defense, what we consider to be a fair comparison for a laboratory called upon to determine a large number of elements under a variety of conditions not necessarily known in advance. 

Luminescence can be defined as the emission of light (intended in the broader sense of ultraviolet, visible, or near infrared radiation) by electronic excited states of atoms or molecules. Luminescence is an important phenomenon from a basic viewpoint (e.g., for monitoring excited state behavior) [1] as well as for applications (lasers, displays, sensors, etc.) [2,3]. 

Absorption ultraviolet-visible (UV-Vis) and fluorescence emission spectra of the aromatic pyrido[l,2-A]pyridazinium cation were measured in buffered aqueous solutions <2002MI37>. 

Measurement techniques that can be employed for the determination of trace metals include atomic absorption spectrometry, anodic stripping voltammetry, differential pulse cathodic stripping voltammetry, inductively coupled plasma atomic emission spectrometry, liquid chromatography of the metal chelates with ultraviolet-visible absorption and, more recently, inductively coupled plasma mass spectrometry. 

Chemiluminescence (CL) is the emission of the electromagnetic (ultraviolet, visible, or near infrared) radiation by molecules or atoms resulting from a transition from an electronically excited state to a lower state (usually the ground state) in which the excited state is produced in a chemical reaction. The CL phenomenon is relatively uncommon because, in most chemical reactions, excited molecules... 

This lamp contains xenon at a fairly high pressure and the light is formed via a discharge across a pair of electrodes. A continuous ultraviolet and visible emission is emitted due to the presence of the xenon. In some instruments, the electronic circuitry creates regular pulses of light that are very intense and therefore more useful. This results in a longer life for the lamp. The intensity varies with wavelength. 

Luminescence is an emission of ultraviolet, visible or infrared photons from an electronically excited species. The word luminescence, which comes from the Latin (lumen = light) was first introduced as luminescenz by the physicist and science historian Eilhardt Wiedemann in 1888, to describe all those phenomena of light which are not solely conditioned by the rise in temperature , as opposed to incandescence. Luminescence is cold light whereas incandescence is hot light. The various types of luminescence are classified according to the mode of excitation (see Table 1.1). 

A fluorescent species is termed a fluorophore or fluor analogous to a chromophore in ultraviolet-visible (UV-vis) specttoscopy. Eluorophores are native chemical species or moieties that exhibit emission upon excitation, often by incident light of the proper wavelength and intensity. Molecular snuctural analysis serves... 

The fluorescence of TPHA 3 is not a mirror image of its absorption spectrum and the emission intensity is sensitive to concentrations greater than 10 M. The excitation profile of 3 also varies with concentration, believed to be due to aggregation of TPHA in solution and only emulates the ultraviolet-visible (UV-Vis) spectrum at concentrations less than 10 M. The Aem decreased from 633 nm in toluene to 619 nm in dimethyl sulfoxide (DMSO), and this is thought to be indicative of a polar ground state and nonpolar excited state <1998JA2989>. 

By fluorescent decay, one refers to the measurement and analysis of the transient ultraviolet, infrared, or visible emissions of a luminescent material following or during excitation. Optical, electronic, nuclear, or X-ray radiations can be used to supply the required energy. 

SOM, soil organic matter HS, humic substances DH, degree of humification HAC, humic acid C FAC, fulvic acid C TEC, total extractable C HR, humification rate HI, humification index NHC, nonhumified C TOC, total organic C HA, humic acid FA, fulvic acids UV-Vis, ultraviolet-visible FT-IR, Fourier transform infrared NMR, nuclear magnetic resonance ESR, electron spin resonance EEM, excitation-emission matrix. 

Ultraviolet-visible (UV-Vis) spectrophotometric detectors are used to monitor chromatographic separations. However, this type of detection offers very little specificity. Element specific detectors are much more useful and important. Atomic absorption spectrometry (AAS), inductively coupled plasma-atomic emission spectroscopy (ICPAES) and inductively coupled plasma-mass spectrometry (ICP-MS) are often used in current studies. The highest sensitivity is achieved by graphite furnace-AAS and ICP-MS. The former is used off-line while the latter is coupled to the chromatographic column and is used on-line . 

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