Laser band width

The dependence of the gadolinium photoion yield at the absorption of the autoionization resonance of 6133.5 A on the pulsed-energy density, E3, of the ionizing laser. Laser band width 0.03 cm 1 (5). 

In experimental measurements, sueh sharp 5-funetion peaks are, of eourse, not observed. Even when very narrow band width laser light sourees are used (i.e., for whieh g(co) is an extremely narrowly peaked funetion), speetral lines are found to possess finite widths. Let us now diseuss several sourees of line broadening, some of whieh will relate to deviations from the "unhindered" rotational motion model introdueed above. 

The modulation transfer function of the optical scatterometer is nearly unity. The spatial frequency band width, using 0.633-nm photons from a He-Ne laser, is typically 0.014—1.6 jim corresponding to a spatial wavelength band width 70— 0.633 pm. This corresponds to near normal sample illumination with a minimum... 

Figure 12.17. (a) Diode laser band structure. (1) In thermal equilibrium. (2) Under forward bias and high carrier injection. Ec, v, and f are the conduction band, valence band, and Fermi energies respectively, (b) Fabry-Perot cavity configuration fora GaAs diode laser. Typical cavity length is 300//m and width 10/tm. d is the depletion layer. 

Figure 10.10 shows the experimental system of TE-CARS microscopy (Ichimura et al. 2004a). As similar to the TERS system (Hayazawa et al. 2000), the system mainly consists of an excitation laser, an inverted microscope, an AFM using a silver-coated probe, and a monochromator. Two mode-locked Ti sapphire lasers (pulse duration 5 picoseconds [ps] spectral band width 4 cm- repetition rate 80 MHz) are used for the excitation of CARS. The (o and (O2 beams are collinearly combined in time and space, and introduced into the microscope with an oil-immersion objective lens (NA = 1.4) focused onto the sample surface. As the z-polarized component of the... 

The pump and probe pulses employed may be subjected to a variety of nonlinear optical mixing processes they may be prepared and characterized by intensity, duration, spectral band width, and polarization. They may arrive in the reaction chamber at a desired time difference, or none. The probe pulse may lead to ionizations followed by detections of ions by mass spectrometry, but many alternatives for probing and detection have been used, such as laser-induced fluorescence, photoelectron spectroscopic detection, absorption spectroscopy, and the like. 

Figure VIII-2 shows the principle of isotope enrichment by two-photon ioni/.ation of 233U atoms. The excitation wavelength is 4266.275 0.02 A. A band width of 0.1 cm 1 is much narrower than an isotope shift of 0.32cm 1. Since the preferentially excited 235U atoms decay in 10-7sec the second laser source to ionize the excited atoms must be pulsed within 10 - 7 sec. The wavelength of the second laser must be shorter than 3777 A, as the combined photon energy must exceed the ionization potential, 6.187 eV, of U atoms. If the first laser is set at 4266.325 A in coincidence with an absorption line of 238U atoms, an isotopic yield ratio of 3000 1 for 238U/23,U is obtained in comparison with 140 1 for the same ratio in the starting material.

H-abstraction intramolecular, 378 Half-value concentration, 181 Half-band width, 69 Half quenching concentration, 173 Hamiltonian operator, 65 perturbing, 67 Hammet equation, 110 He-Ne laser, 318 Heavy atom perturbation, 70 external, 145 intermolecular, 71 intramolecular, 71... 

Pressed pellets of BaTiC>3 were sintered in a platinum dish for six hours at 900°C in a controlled partial pressure of oxygen. The samples were quenched to room temperature, and the spectra recorded on a four-slit double-monochromator Raman spectrophotometer. An Ar+ laser with excitation at 514.5 nm was the source. The spectra were recorded at room temperature. Figure 4-30 shows the spectrum of BaTiC>3 whose Ba/Ti ratio is equal to 0.9999. The Raman spectrum is sensitive to the Ba/Ti ratio and theoxygen non-stoichiometry. The half-band width is variable as well as the intensity ratio of the 525 and 713 cm-1 bands. The ratio (I525/713) is at a minimum at the composition of 0.9999, and this can be observed in Fig. 4-31, which shows a plot of the intensity ratio (I525//713) vs. the Ba/Ti composition. 

FIG. 4.8. (a) CBP perylene high quality blue laser emission with very narrow band width [105]. (b) Emission spectra of CW InGaN MQW laser diode with two different operating currents at RT [171]. 

Since that time, laser photochemistry has become a popular subject and with it have come the laser photochemists looking for a photon target. Obviously, the first laser photons would be aimed toward isotope separations which required the narrow band-widths which the laser so uniquely provided but spin-off targets have since included the separations of reactor fuel components in reprocessing and/or waste isolation systems. Although much has been promised from the application of lasers to the reprocessing of nuclear fuels, there has been very little evidence that would... 

Thus, in the case of parallel dipole moments the spectrum is composed of two lines of equal band widths ( F) located at frequencies %/ A2 + 21 i2 and there is no the central component in the fluorescence spectrum at the laser frequency a>i. The eigenvalue X = 0 contributes to the coherent scattering of the laser field. When Ti2 = 0, the spectrum is composed of three lines the central line of the bandwidth i T located at the laser frequency and two sidebands of band widths [ ... 

Oscillator strengths or absorption cross sections may be obtained by applying saturation spectroscopy techniques to multistep photoionization spectroscopy. A few transitions in uranium have been studied.One of the advantages of saturation spectroscopy is that it can be applied to any one of the steps in the schemes shown in Fig. 2. The disadvantages are that the experimental requirements are severe (laser-atomic beam interaction area,-frequency,-band width and-polarization) and interpertation of the data can be complex. A detailed discussion will not be given because little application has been made to the lanthanides and actinides. We will discuss in the Autoionization section the determination of photoionization cross sections by a saturation method. 

The measurement of isotope shifts and hyperfine structure (hfs) is possible in multistep laser excitation and ionization if one of the excitation lasers in the excitation schemes shown in Fig. 2 is a narrow band laser and if a collimated atomic beam is used as the source of absorbing atoms. The rest of the aparatus can remain as used for other studies. The narrow band laser(s) may be a pressure tuned pulsed dye laser ( 100 MHz, 0.003 cm l) or a CW dye laser (30 MHz to 30 KHz, 10- to 10 6 cm-- -). The atomic beam should be collimated to reduce "Doppler" broading to the level required to attain the resolution needed for investigating the structure and to fully utilize the narrow band width of the laser. A band width of 10cm-- - is usually adequate for most investigations of lanthanides and actinides. A portion of the scan laser beam is directed to an etalon and detector (interferometer) to provide relative frequency calibration. 

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