Linewidth, atomic

The master equation (97) with parameters (98) is quite general in terms of the matching of the squeezed modes to the vacuum modes and the bandwidth of the squeezed field relative to the atomic linewidths. The master equation is in the... 

High-resolution spectroscopy used to observe hyperfme structure in the spectra of atoms or rotational stnicture in electronic spectra of gaseous molecules connnonly must contend with the widths of the spectral lines and how that compares with the separations between lines. Tln-ee contributions to the linewidth will be mentioned here tlie natural line width due to tlie finite lifetime of the excited state, collisional broadening of lines, and the Doppler effect. 

The absolute measurement of areas is not usually usefiil, because tlie sensitivity of the spectrometer depends on factors such as temperature, pulse length, amplifier settings and the exact tuning of the coil used to detect resonance. Peak intensities are also less usefiil, because linewidths vary, and because the resonance from a given chemical type of atom will often be split into a pattern called a multiplet. However, the relative overall areas of the peaks or multiplets still obey the simple rule given above, if appropriate conditions are met. Most samples have several chemically distinct types of (for example) hydrogen atoms within the molecules under study, so that a simple inspection of the number of peaks/multiplets and of their relative areas can help to identify the molecules, even in cases where no usefid infonnation is available from shifts or couplings. 

These values show some dependence on concentration, pH and temperature. Note also the much smaller linewidth for the central, symmetrically 4-coordinated Al atom of the tridecameric AI13 species when compared with that of the twelve less symmetrically coordinated octahedral Al atoms, and the possibility of extracting a reasonably precise value of for this latter resonance which has a linewidth of some 8000 Hz. 

LLNL AVLIS Laser. The first WFS measurements using a Na LGS were performed at LLNL (Max et al., 1994 Avicola et al., 1994). These experiments utilized an 1100 W dye laser, developed for atomic vapor laser isotope separation (AVLIS). The wavefront was better than 0.03 wave rms. The dye laser was pumped by 1500 W copper vapor lasers. They are not well suited as a pump for LGSs because of their 26 kHz pulse rate and 32 ns pulse length. The peak intensity at the Na layer, with an atmospheric transmission of 0.6 and a spot diameter of 2.0 m, is 25 W/cm, 4x the saturation. The laser linewidth and shape were tailored to match the D2 line. The power was varied from 7 to 1100 W on Na layer to study saturation. The spot size was measured to be 7 arcsec FWHM at 1100 W. It reduced to 4.6 arcsec after accounting for satura-... 

Table I reports the observed NMR linewidths for the H/3 protons of the coordinating cysteines in a series of iron-sulfur proteins with increasing nuclearity of the cluster, and in different oxidation states. We have attempted to rationalize the linewidths on the basis of the equations describing the Solomon and Curie contributions to the nuclear transverse relaxation rate [Eqs. (1) and (2)]. When dealing with polymetallic systems, the S value of the ground state has been used in the equations. When the ground state had S = 0, reference was made to the S of the first excited state and the results were scaled for the partial population of the state. In addition, in polymetallic systems it is also important to account for the fact that the orbitals of each iron atom contribute differently to the populated levels. For each level, the enhancement of nuclear relaxation induced by each iron is proportional to the square of the contribution of its orbitals (54). In practice, one has to calculate the following coefficient for each iron atom ...

Fe Q-band ENDOR study of the isotopically enriched Ni-C state of D. gigas and D. desulfuricans hydrogenases and Ni-B state of D. desulfuricans revealed a weak coupling between the Fe and the nickel atoms when the enzyme was in the Ni-A forms while no coupling was observed for the Ni-B form (186). A careful analysis of linewidth of Ni-A and Ni-B EPR signals detected in Fe enriched and nonenriched hydrogenase samples indicated that hyperfine interactions are lost in the spectral linewidth and, hence, nonde-tectable. 

It is well known that solid materials are characterized by lack of relative motion between the constituent atoms compared with liquids, which results in NMR linewidths much broader than for liquids. Also, it often happens that solids have much longer spin-lattice relaxation 7 than in liquid samples. Thus, studying NMR of solids is more difficult than liquids and studying flows of solid material would seem to be quite impractical. 

Fig. 6 mCd NMR chemical shifts (diamonds) and linewidths (triangles) of Cd, YZ.nYTc as a function of x. The dashed-dotted line is the most probable number of NNN Zn atoms, and the solid line is the width calculated from probability distributions. Reprinted with permission from [157]. Copyright 1987 by the American Physical Society... 

Linewidth The spread in wavelengths or frequencies associated with a transition in an atom or molecule. There are three contributions natural linewidth associated with the lifetime of the transition pressure broadening associated with the presence with the other molecules nearby Doppler broadening associated with relative motion of the molecule and light source. 

On the basis of the observations mentioned above, we conclude that the vibration at 1875 cm-1 is a Si—H vibration. This follow from (1) the sharpness of the feature, linewidth less than 50 cm-1, and (2) the frequency relative to the range of measured B—H and Si—H frequencies. Figure 15 presents a model for the local bonding configuration involving the H atom. This model accounts for the frequency of vibration as well... 

Figure 5.1 Resonant absorption of y-radiation by a nucleus can only take place in the solid state because of recoil effects. The excited nucleus of a free atom emits a y-photon with an energy EirER, whereas the nucleus in the ground slate of a free atom can only absorb a photon if it has an energy equal to Eo+ER. As the linewidth of nuclear transitions is extremely narrow, the emission spectrum does not overlap with the absorption spectrum. In a solid, a considerable fraction of events occurs recoil free (ER=0), and here the emission spectrum overlaps completely with the absorption spectrum (provided source and absorber have the same chemical environment).

In gases (atomic or ionic) the electronic energy levels of free atoms are narrow, since they are diluted systems and perturbation by the surroundings is very weak. An important fact derived from the discrete nature of the electronic levels in a gas is the high monochromaticity of the laser lines in this type of laser, compared to that of solid-medium based lasers. The high degree of coherence achievable with gas lasers is also a characteristic feature related to the narrow linewidth. 

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