Energy spectrum, nonresonant

Fig. 3.18 Pulse-height analysis (PHA) spectrum (or energy spectrum) for Co/Rh Mossbauer source radiation backscattered nonresonantly and/or resonantly from aluminum and stainless steel plates. Data were obtained with Si-PIN diodes with sensitive area of 1 cm per diode and a thickness of 400 pm (from [36, 46])...

The complexity of the Co emission spectrum and the low fraction of the desired 14.4 keV radiation require an efficient Mossbauer counting system that is able to discriminate photons of different energies and reject the unwanted events. Otherwise a huge nonresonant background would add to the counting statistics of the spectra and fatally increase the noise of the spectrometer. 

Fig. A.l Contributions to a Mossbauer transmission spectrum. N, is the nonresonant background from scattered high-energy y-radiation and X-ray fluorescence in the source and the absorber...

In resonant Raman spectroscopy, the frequency of the incident beam is resonant with the energy difference between two real electronic levels and so the efficiency can be enhanced by a factor of 10 . However, to observe resonant Raman scattering it is necessary to prevent the possible overlap with the more efficient emission spectra. Thus, Raman experiments are usually realized under nonresonant illumination, so that the Raman spectrum cannot be masked by fluorescence. 

Fig. 6.8. A Principle of frequency-multiplexed CARS microspectroscopy A narrow-bandwidth pump pulse determines the inherent spectral resolution, while a broad-bandwidth Stokes pulse allows simultaneous detection over a wide range of Raman shifts. The multiplex CARS spectra shown originate from a 70 mM solution of cholesterol in CCI4 (solid line) and the nonresonant background of coverglass (dashed line) at a Raman shift centered at 2900 cm-1. B Energy level diagram for a multiplex CARS process. C Schematic of the multiplex CARS microscope (P polarizer HWP/QWP half/quarter-wave plate BC dichroic beam combiner Obj objective lens F filter A analyzer FM flip mirror L lens D detector S sample). D Measured normalized CARS spectrum of the cholesterol solution. E Maximum entropy method (MEM) phase spectrum (solid line) retrieved from (D) and the error background phase (dashed line) determined by a polynomial fit to those spectral regions without vibrational resonances. F Retrieved Raman response (solid line) calculated from the spectra shown in (E), directly reproducing the independently measured spontaneous Raman response (dashed line) of the same cholesterol sample...

Spectroscopic observables can be categorized in several ways. We can follow a temporal profile or a frequency resolved spectrum we may distinguish between observables that reflect linear or nonlinear response to the probe beam we can study different energy domains and different timescales and we can look at resonant and nonresonant response. This chapter discusses some concepts, issues, and methodologies that pertain to the effect of a condensed phase environment on these observables. For an in-depth look at these issues the reader may consult many texts that focus on particular spectroscopies. ... 

Change in the refractive index can be induced by either a resonant or a nonresonant process. For a resonant process, the frequency of the incident light overlaps with an electronic absorption band, by either a one-photon or a multiphoton process. The energy is absorbed by the sample and an excited state population is generated. This induces a transient change in the absorption spectrum of the material due to the bleaching of the ground state absorption and/or the appearance of the excited state absorption. A nonlinear absorption coefficient a2 can be defined similarly to Eq. (15) ... 

These properties were utilized in the study of energy transfer from NO to a variety of accepting molecules. Acceptors whose one-photon absorption spectrum strongly overlaps that of NO were investigated for the first time. Efficiency of resonant and nonresonant processes could thus be empirically compared. A unified mechanism, involving a charge transfer intermediate, was found to account reasonably well for all the observed rate constants. 

If it is nonresonant, the transfer is accompanied by vibrational excitations in order to ensure energy conservation. A transfer time is clearly defined. Most importantly, the spectrum of the individual chromophore is not changed. In disordered systems, stochastic energy transport is always accompanied by fluorescence depolarization. 

The following free parameters were introduced (1) energy of the band head, (2) absolute intensity of the band, and (3) rotational parameter of the band. The last parameter was kept identical for all of the groups, i.e., the 5.28, 5.37 and 5.47 MeV groups. A fit to the measured spectrum was performed with the above parameters using the least squares method. The nonresonant part of the fission probability was taken into account as an exponential background. ... 

Figure 2. Energy-loss spectrum of neutralized Cs atoms, on top of the hyperfine structure of Cs (6s Sif2-lp 3/2), for different Cs vapor pressures in the charge-exchange cell (1) resonant charge transfer, (2) nonresonant charge transfer and collisional excitation 6s 6p, (3) and (4) multiple excitation 6s 6p.

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