Halfwidth temperature dependence

Ryason and Russel measured the temperature dependence of the IR absorption band halfwidth for valence vibrations of hydroxyl groups on the silica surface.200 At T > 325 K, the least squares method permits a straight line to be drawn through experimental points of the dependence In Avv2 (Tl), the equation of the line appearing as follows 200... 

Fig. A2.2. Temperature dependences measured for the haliwidths Av n of the IR absorption bands for valence vibrations of OH(D) groups on Si02 surface (filled markers) and recalculated for the halfwidths w of three components of Lorentzian lines (empty markers) for OH (1) and (OD) groups of high concentration (2), and for (OD) groups of low concentration (3).2"2...

Among other new methods, tunable laser absorption spectroscopy using infrared diode lasers offers prospects for improved accuracy and specificity in concentration measurements, when a line-of-sight technique is appropriate. The present paper discusses diode laser techniques as applied to a flat flame burner and to a room temperature absorption cell. The cell experiments are used to determine the absorption band strength which is needed to properly interpret high temperature experiments. Preliminary results are reported for CO concentration measurements in a flame, the fundamental band strength of CO at STP, collision halfwidths of CO under flame conditions, and the temperature dependence of CO and NO collision halfwidths in combustion gases. 

The temperature dependence of the collision halfwidth, 2y(T), is of fundamental and practical interest and has not previously been investigated at elevated temperatures. In the past, most determinations of collision halfwidth have been made near room temperature, and high-temperature values have been obtained by extrapolation, usually assuming a T 0>5 temperature dependence so that... 

The temperature dependence of the collision halfwidth for combustion gas broadening is also of interest. Results for specific transitions in CO and NO are given in Table I. In the... 

The pressure and temperature dependence of the halfwidth parameter 7. is given by... 

Any temperature dependence of the CEF halfwidth can be attributed to either s-f interaction or the interaction of f states with phonons, s-f line broadening for simple metals has been attributed to the effects of the carrier spin dynamics on the CEF-state lifetimes and has been described by the Fermi liquid theory, introduced by Becker et al. (1977). The s-f interaction Hamiltonian describing the coupling between the 4f electrons and the conduction electrons can be written as... 

Fig. 87. Neutron-diffraction measurements of Euo 5jSr 4gS single crystal (a) Elastic scans measured at (2+ qijO, 0). The curve through the r = 6K data is a resolution-limited Gaussian. For 7 <6K the solid line represents fits to the data using eq. 101, and the dashed line indicates the Lorentzian (non-Bragg) part of the scattering, (b) Temperature dependence of Lorentzian amplitude A and halfwidth k obtained from the fits shown in part (a). The limits of instrumental resolution in q are indicated (from Maletta et al. 1982b).

Hie temperature dependence of a homogeneous linewidth resulting from the two-phonon, two-tunnelon and tunnelon-phonon processes are sdiematicaUy depicted in Fig. 33. It should emphasize that only two-tunnelon processes ate able to cause the saturation effects in the temperature dependence of homogeneous halfwidths. We shall use this fact when interpretating experimental data. 

Fig. 33a-c. Temperature dependence of a homogeneous halfwidth y = I/T2 due to a tn > dK>non, b tunndon )honon and c two-tunnelon Raman-like debasing vocesses. Only the two-tunnelon process leads to the plateau in the high temperature range... 

Results showing the dependence of the CO collision halfwidth in combustion gases on the vibrational and rotational quantum numbers are shown in Figure 6. The data were obtained with a flame temperature of 1875 K and equivalence ratios in the range 1.2 - 1.4. Although too few data points are available for a detailed analysis, it is clear that 2y decreases with increasing m and that values for 2y are nearly equal (within 5%) for ground state and excited state transitions. 

Figure 4.71 presents typical laser-induced luminescence spectra recorded from natural barite with orange luminescence. At room temperature under 308, 337 and 355 nm excitations orange luminescence consists of very broad band peaking at 635 nm with half-width of approximately A = 150 nm (Fig. 4.71a). At lower temperatures up to liquid helium the spectrum is very similar and only the halfwidth of A = 130 nm becomes a httle narrower (Fig. 4.71b). At all temperatures the spectra are not depending on delay times and gate widths. The possible conclusion is that only one luminescence center is responsible for this orange band. Decay time of luminescence is approximately 225 ps at 300 K and 275 ps at 4.2 K.

The growth of both temperature and coupling constant, leads to the disappearance of ZPL. In this case, the absorption and fluorescence bands are Gaussian. The distance between their maxima equals 2A and it is called Stokes shift. It does not depend on temperature. On the contrary, the Gaussian halfwidths A[Pg.136]

Since the temperature cycling experiments take a long time the irreversible hole width measured in these experiments can be due both to thermal-induced SD and to spontaneous SD. The latter depends on time. Experiments by the Payer group [83] prove this statement. Their experimental data plotted in Fig. 28 show the SD effect which manifests itself in the time-related increase in the width of holes burnt at various temperatures. However, if the hole burnt at Tb = 1.3 K is subjected to a temperature cycle Tb T Tb the hole acquires an additional halfwidth. This excess of halfwidth is due mainly to spontaneous SD which depends ordy on the duration of the experiment. Tte thermally-induced SD does not contribute to the result of this temperature cycling experiment In the light of these results, we can assume that some of the irreversible halfwidth plotted in Fig. 25 is due to a spontaneous SD and does not depend on the value of a temperature excursion. 

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