Photon spectrum

Figure 9.51 A zero kinetic energy photoelectron (ZEKE-PE) resonant two-photon spectrum of 1,4-difluorobenzene in which the first photon excites the molecule of the zero-point level of the S-[ excited electronic state of the molecule. (Reproduced, with permission, from Reiser, G., Rieger, D., Wright, T.G., Muller-Dethlefs, K. and Schlag, E.W., J. Phys. Chem., 97, 4335, 1993)...

Photons, Compton-scattered, 21 312 Photon spectrum, 21 296 Photon stimulated desorption (PSD), 24 74 Photooxidation, 9 385-386 dye-induced, 19 195 in industry, 9 518 reactions, 9 515-518 Photooxidative degradation... 

In BIS, the process (2) is reversed, and we analyze, as said before, the photon spectrum yielded by the system as Bremsstrahlung when electrons occupy empty states. 

Figure 6.9 Generic five-state system for ultrafast efficient switching. The resonant two-state system of Figure 6.6 is extended by three target states for selective excitation. While the intermediate target state 4) is in exact two-photon resonance with the laser pulse, both outer target states 3) and 5) lie well outside the bandwidth of the two-photon spectrum. Therefore, these states are energetically inaccessible under weak-field excitation. Intense femtosecond laser pulses, however, utilize the resonant AC Stark effect to modify the energy landscape. As a result, new excitation pathways open up, enabling efficient population transfer to the outer target states as well.

Again, since the d orbitals have even parity, even if the molecule does not have an inversion center there is an approximate selection rule in which transitions that would be g -> g (or u -> u) in a parent group with inversion symmetry are allowed. The odd parity vibrations that dominate the single photon spectrum are forbidden, while the even parity vibrations are allowed, but have no advantage over the pure electronic transitions. Experimental two-photon spectra of the sharp-line transitions of Mn4+ in a Cs2Ge F6 host confirm both the simplicity of the spectrum and the relative prominence of the 0-0 lines [55],... 

In the two-photon spectrum in Figure 9.29 the vibrations v18a,v17b, v16a and v15 have symmetry species b u, b2u, au and b2u, respectively. Show that the 18ag, 17b,1,. 16a,1, and 15 0 transitions are allowed by symmetry. 

Fig. 5. Composite 15-2,S two-photon spectrum of trapped hydrogen after condensation. o-spectrum of sample without a condensate -spectrum emphasizing features due to a condensate. The high density in the condensate shifts a portion of the Doppler-free line to the red. The condensate s narrow momentum distribution gives rise to a similar feature near the center of the Doppler-sensitive line...

Fig 8 a) Doppler-free two-photon spectrum of the sodium 3S to 4D transition taken with a single frequency dye laser, b) The same transition observed using an FM dye laser. 

Fig. 4. Resonance enhanced, three-photon spectrum of atomic oxygen, observed...

Fig. 5. Resonance enhanced, two-photon spectrum of rotationally relaxed NO produced in reaction (18) initiated by the KrF laser...

CNDO/S Cl calculation of two-photon spectrum of pyrene. Vibronic activity of some 6, and bju vibrational bands... 

Figure 7 shows the photon spectrum from Cs and sources. They were obtained with a 1 cm pure Csl crystal at 117 K coupled to the photodiode with optical silicon grease. The light output was 26,000 photons/MeV, leading to an r.m.s energy resolution of less than 6 % for 511 keV photons. To our knowledge such a performance as not been achieved so far. 

Pyridine is another molecule of enduring interest. The two photon spectrum of liquid pyridine has been obtained by thermal lensing techniques. The two lowest htt states are of benzene type and the next higher excited state is nir. The fluorescence of the trajTS - 2 - s tyr ylqu inoxaline conformer has been found to change markedly with solvent. The photophysics of 6-(2/-hydroxy-4 -methoxyphenyl)-s-triazine photostabilizer has been examined in... 

As an example of the use of two-photon spectroscopy in assigning excited states that are not observed in one-photon UV spectroscopy, the two-photon absorption spectrum of naphthalene is shown in Figure 1.17. Since for the point group all Bg states have a theoretical polarization degree of H = 3/2, the polarization measurement reveals immediately a Bg state near 42,000 cm . In the two-photon absorption spectrum this shows up only as a shoulder, whereas the maximum at 44,500 cm" can be assigned to an Ag state. Neither state is prominent in the one-photon spectrum. 

Figure 1.18. Part of the two-photon spectrum of benzene at different resolutions a) vibrational structure of the S - S transition, b) Q branch of the most intense vibrational line (I4i) with a resolution 5v limited by the Doppler broadening, and c) elimination of the Doppler broadening which yields individual rotational lines (by permission from Neusser and Schlag, 1992).

We assume that the pulse is long (Rjj 1) and the molecule has time to relax to the lowest vibrational level of the electronic level z. The case of short pulse differs qualitatively as illustrated in Fig. 13. First of all we simulated the spectra of one-photon (Fig. 14) and coherent two-photon absorption, (Fig. 15). One can see that the one-photon spectrum consists of two vibrational bands related to transitions to the first (0 1) and the fourth (0 4) elec-... 

Unlike metabolism in a reducing world, oxidizing metabolism must build biomatter from substrates of lower free energy anabolism and catabolism are opposed. Thus, only in the presence of a non-equilibrium photon spectrum is oxidizing metabolism a relaxation process. 

All these characteristics can be seen in Fig. 13 where a portion of the TPA polarised spectrum of Cs2U02Cl4 is compared with a single-photon polarised spectrum [40], The spectrum is particularly easy to interpret, and in its entirety confirms the location of the 12 states previously proposed from the analysis of the one-photon spectrum. In particular strong origin bands are found where previously the existence of the electronic excited states had to be inferred from an analysis of the vibronic structure. But in addition, TPA locates two further excited states in the near ultraviolet which were previously unknown, making a total of 14 excited states. 

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