Atomic spectra, origin

Figure 4.12 The origin of Zeeman splitting in the n = 2-n = 3 transition in the H atomic spectrum...

NEXAFS. A narrow sweep just above the core-level edge displays characteristic peaks in the spectrum that can serve as a fingerprint of the chemical bonding around the atom of origin. 

The explanation of the hydrogen atom spectrum and the photoelectric effect, together with other anomalous observations such as the behaviour of the molar heat capacity C of a solid at temperatures close to 0 K and the frequency distribution of black body radiation, originated with Planck. In 1900 he proposed that the microscopic oscillators, of which a black body is made up, have an oscillation frequency v related to the energy E of the emitted radiation by... 

The use of the words term and state is not so clear cut. The word term was originally used in the early days of spectroscopy in the sense of Equation (1.4), where the frequency of a line in an atomic spectrum is expressed as the difference between two terms which are simply terms in an equation. 

Line spectrum originating from excited atoms or atomic ions (excluding poly atomic ions or radicals). These spectra consists of distinct and often widely spaced lines. 

Different ECP approaches can be classified according to various criteria. If the original radial-node structure of the atomic valence orbitals is preserved, a model potential is produced [808-813]. If the nodal structure is not conserved, the ECP is called pseudo potential [814-817], While shape-consistent pseudo potentials [818-821] are optimized to obtain a maximum resemblance in the shape of pseudo-valence orbitals and original valence orbitals, energy-consistent pseudo potentials [822-829] reproduce the experimental atomic spectrum very accurately. 

A magnetic dipole interaction between the magnetic moment of the nucleus and the internal field (intrinsic or extrinsic to the atom in origin). The result is a multiple line structure in the spectrum known as magnetic hyperfine splitting, and labelled Bht see Figure 4.45b. 

Metal nanoparticles have been studied mainly because of their unique optical properties especially nanoparticles of the noble metals copper, silver, and gold have a broad absorption band in the visible region of the electromagnetic spectrum. Solutions of these metal nanoparticles show a very intense color, which is absent in the bulk material and atoms. The origin of the intense color of noble metal nanoparticles is attributed to the collective oscillation of the free conductive electrons induced by an interacting electromagnetic field. These resonances are also denoted as siuface plasmons [15]. 

There is a small peak one mass unit higher than M m the mass spectrum of ben zene What is the origin of this peak d What we see m Figure 13 40 as a single mass spectrum is actually a superposition of the spectra of three isotopically distinct benzenes Most of the benzene molecules contain only and H and have a molecular mass of 78 Smaller proportions of benzene molecules contain m place of one of the atoms or m place of one of the protons Both these species have a molecular mass of 79... 

Normal ions (M+, Fj+,. .., F +) in a spectrum can provide a molecular structure for substance M if the fragments can be theoretically reassembled. The problem is rather like deducing an original jigsaw puzzle by putting the pieces together correctly. For most molecules containing more than a few atoms, this reassembly exercise is difficult and often problematic. 

Gelbart (1974) has reviewed a number of theories of the origins of the depolarized spectrum. One of the simplest models is the isolated binary collision (IBC) model of McTague and Bimbaum (1968). All effects due to the interaction of three or more particles are ignored, and the scattering is due only to diatomic collision processes. In the case that the interacting particles A and B are atoms or highly symmetrical molecules then there are only two unique components of the pair polarizability tensor, and attention focuses on the anisotropy and the incremental mean pair polarizability... 

The resulting emission spectrum thus consists of lines originating from excited atoms or ions. These processes are conveniently represented diagrammatically as in Fig. 21.1. 

The example of COj discussed previously, which has no vibrations which are active in both the Raman and infrared spectra, is an illustration of the Principle of Mutual Exclusion For a centrosymmetric molecule every Raman active vibration is inactive in the infrared and any infrared active vibration is inactive in the Raman spectrum. A centrosymmetric molecule is one which possesses a center of symmetry. A center of symmetry is a point in a molecule about which the atoms are arranged in conjugate pairs. That is, taking the center of inversion as the origin (0, 0, 0), for every atom positioned at (au, yi, z ) there will be an identical atom at (-a ,-, —y%, —z,). A square planar molecule XY4 has a center of symmetry at atom X, whereas a trigonal planar molecule XYS does not possess a center of symmetry. 

Actually Schrddinger s original paper on quantum mechanics already contained a relativistic wave equation, which, however, gave the wrong answer for the spectrum of the hydrogen atom. Due to this fact, and because of problems connected with the physical interpretation of this equation, which is of second order in the spaoe and time variables, it was temporarily discarded. Dirac took seriously the notion of first... 

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