Transitions ultraviolet emission

The divalent rare-earth ion Eu has the 4f electronic configuration at the ground states and the 4f 5d electronic configuration at the excited states. The broadband absorption and luminescence of Eu are due to 4f - 4 f 5d transitions. The emission of Eu is very strongly dependent on the host lattice. It can vary from the ultraviolet to the red region of the electromagnetic spectrum. Furthermore, the 4f-5d transition of Eu decays relatively fast, less than a few microseconds [33]. 

Structure. The ultraviolet emission spectrum of CF2 was first examined by Venkateswarlu 2 9, who prepared the molecule by passing an uncondensed transformer discharge through CF4. An extensive band system between 3250 and 2400 A was observed. The similarity of the band system to that of N02 suggested that a non-linear triatomic molecule was responsible for the spectrum. Venkateswarlu identified the band system with the transition 1B2 - 1 Aj. 

The work of Neuimin and Terenin86 on the photolysis of water is to be regarded as classical. They studied the near ultraviolet emission produced when H20 is subjected to vacuum ultraviolet radiation from a hydrogen discharge. They associated the emission correctly with an electronic transition of the OH free radical. The energetics of the dissociation of water are presented in Table XII. 

The formula of the first host lattice has been given as Mg28Ge7.503sFio- The Mn + ion (34 configuration) absorbs over the whole ultraviolet range with an intense charge-transfer transition. The emission is in the deep red (620-670 nm), consists of several lines, and is due to the E -> transition (Sect. 3.3.4b). Thermal quenching occurs only above 3(X)°C as is to be expected for a narrow line emission. The decay... 

Ce and Eu usually shows a typical broadband emission accompanied by intense broad absorption from the 5ii-4/transitions. Their emission positions can vary from ultraviolet to red, and their corresponding excitation positions can also be tuned from ultraviolet to blue light, which depends on the crystal field strength of the host matrix. Therefore, Ce " and Eu " ion are efficient sensitizers and can transfer part of their energy to activator ions. In recent years, numerous single-phased multicolor-emitting phosphors have been developed based on the energy transfer from Ce " or Eu to activators such as Mn / Eu / Tb ", Dy / Pr / and so on. 

In the present review, we discuss in section 2 the effects of rotational coupling on the intensities of Lyman and Werner band systems of the vacuum ultraviolet emission spectrum of Hj towards discrete as well as continuous states of the ground X level of H,. In section 3 we present theoretical calculations by D. Gerlich on the reactive scattering of H + (leading to ortho-para transitions in H ) and its deuterated analog D + - HD + H . Section 4 is devoted to recent theoretical calculations on collisional... 

The vacuum ultraviolet emission spectrum of solid argon doped with nitrogen showed a broad band with a maximum at 163 nm which is attributed to a transition from an ArN exciplex to the unbound ground state This band has its maximum intensity at... 

Most of the material in molecular clouds is in the form of H2, which owing to its lack of a permanent dipole moment has no easily observable rotational transitions. It can be observed through rovibrational and fluorescent transitions, but only within environments which are very specific, such as shocks and regions containing high levels of ultraviolet emission. Therefore, the principal component of molecular clouds is effectively unmeasurable. This fact forces astronomers to use trace constituents, other molecules and dust, to measure the physical conditions in molecular clouds. 

Optical metiiods, in both bulb and beam expermrents, have been employed to detemiine tlie relative populations of individual internal quantum states of products of chemical reactions. Most connnonly, such methods employ a transition to an excited electronic, rather than vibrational, level of tlie molecule. Molecular electronic transitions occur in the visible and ultraviolet, and detection of emission in these spectral regions can be accomplished much more sensitively than in the infrared, where vibrational transitions occur. In addition to their use in the study of collisional reaction dynamics, laser spectroscopic methods have been widely applied for the measurement of temperature and species concentrations in many different kinds of reaction media, including combustion media [31] and atmospheric chemistry [32]. 

Promotion of an electron in Hc2 from the (7 15 to a bonding orbital produces some bound states of the molecule of which several have been characterized in emission spectroscopy. For example, the configuration ((J l5 ) ((7 l5 ) ((7 25 ) gives rise to the 2i and bound states. Figure 7.24(a) shows the form of the potential curve for the state. The A-X transition is allowed and gives rise to an intense continuum in emission between 60 nm and 100 nm. This is used as a far-ultraviolet continuum source (see Section 3.4.5) as are the corresponding continua from other noble gas diatomic molecules. 

Only electron transitions down to the second orbit cause emission of visible light. Other transitions may involve infrared or ultraviolet light. 

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... 

Both absorption and emission may be observed in each region of the spectrum, but in practice only absorption spectra are studied extensively. Three techniques are important for analytical purposes visible and ultraviolet spectrometry (electronic), infrared spectrometry (vibrational) and nuclear magnetic resonance spectrometry (nuclear spin). The characteristic spectra associated with each of these techniques differ appreciably in their complexity and intensity. Changes in electronic energy are accompanied by simultaneous transitions between vibrational and rotational levels and result in broadband spectra. Vibrational spectra have somewhat broadened bands because of simultaneous changes in rotational energy, whilst nuclear magnetic resonance spectra are characterized by narrow bands. 

The absorption and emission of radiation in the near ultraviolet (UV) and visible regions of the electromagnetic spectrum are associated with electronic (and associated vibronic) transitions involving n- and/or n-electron systems of molecules. Synthetic and natural polymers absorb in the UV region and particularly strong absorption spectra are recorded for polymers containing aromatic and heteroaromatic groups (e.g., poly(styrenes), poly(vinyl naphthalenes), poly(vinyl carbazoles)). 

Atomic emission spectroscopy is one of the oldest instrumental techniques used for chemical analysis. It is used to study the transitions between electronic energy levels in atoms or ions. These energy differences are usually in the visible region (400-700 nm) of the electromagnetic spectrum, but if the energy difference is larger, then the transitions may lie in the ultraviolet region. 

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