Double resonance Raman process

Fig. 9. 23 (a) Representation of a double resonance Raman process that gives rise to the D band, (b) Schematic illustration of the atomic stmcture of the edges, (c) Double resonance mechanism for an armchair edge [50]... 

Fig. 9.8 Vibration of A/ phonon mode and the double resonance Raman scattering process for the 2D band...

Fig. 9.13 (a-d) Schematic view of the electron dispersion of bilayer graphene near the K and K points showing both 7ti and 7t2 bands. The four double resonance Raman scattering processes are indicated. The wave vectors of the electrons ( i, 2. and k-l) involved in each of these four processes are also indicated [27]. (e) Typical 2D band spectrum with the four components is indicated... 

Fig.1 A schematic representation of process in double-resonant Raman scattering [6]...

The D-band is a disorder-induced feature arising from double resonance Raman scattering process from a non-zero-centre phonon mode. It is also an... 

The first laser Raman spectra were inherently time-resolved (although no dynamical processes were actually studied) by virtue of the pulsed excitation source (ruby laser) and the simultaneous detection of all Raman frequencies by photographic spectroscopy. The advent of the scanning double monochromator, while a great advance for c.w. spectroscopy, spelled the temporary end of time resolution in Raman spectroscopy. The time-resolved techniques began to be revitalized in 1968 when Bridoux and Delhaye (16) adapted television detectors (analogous to, but faster, more convenient, and more sensitive than, photographic film) to Raman spectroscopy. The advent of the resonance Raman effect provided the sensitivity required to detect the Raman spectra of intrinsically dilute, short-lived chemical species. The development of time-resolved resonance Raman (TR ) techniques (17) in our laboratories and by others (18) has led to the routine TR observation of nanosecond-lived transients (19) and isolated observations of picosecond-timescale events by TR (20-22). A specific example of a TR study will be discussed in a later section. 

Fig. 7.3 (a) 2D Brillouin zone of graphene showing characteristic points K and T and Dirac cones located at the six comers (K points), (b) Second-order double resonance scheme for the D peak (close to F) (c) Raman spectral process for the D peak (involving two neighboring K points of the Brillouin zone K and K ). El is the incident laser energy. (After Ref. [46, 48])... 

In addition, CNTs exhibit several Raman features whose frequencies change with changing excitation wavelength. A prominent example for this unusual behavior is the disorder-induced D band which results from a defect-induced double-resonant process [46]. In the molecular picture, the D band originates from the breathing vibrations of aromatic rings in the honeycomb lattice. A quantitative description of the D band intensity in graphene was recently derived by Sato et al. 

Recently, a novel rf-laser double resonance method for optical heterodyne detection of sublevel coherence phenomena was introduced. This so-called Raman heterodyne technique relies on a coherent Raman process being stimulated by a resonant rf field and a laser field (see Fig.l(a)). The method has been applied to impurity ion solids for studying nuclear magnetic resonances at low temperature3 5 and to rf resonances in an atomic vapor /, jn this section we briefly review our results on Raman heterodyne detection of rf-induced resonances in the gas phase. As a specific example, we report studies on Zeeman resonances in a J=1 - J =0 transition in atomic samarium vapor in the presence of foreign gas perturbers. 

Optical-Optical double resonance (PPOODR), and the lambda technique could also be called pump-dump optical-optical double resonance (PDOODR), or a stimulated Raman process. The lambda approach is the focus of Chapters 6, 7, and 8, because formation of ultracold X- and a-state molecules is the goal. The critical difference compared to ordinary OODR is that the initial state is a continuum state (albeit with an ultracold kinetic energy). 

Computationally, the X-ray Raman process has been addressed by both time-dependent and time-independent methods. In the latter case the properties of resonant X-ray spectra (RXS) are guided by the double-differential cross section [233, 234]... 

When the two beams of pump laser and probe laser in the double resonance scheme of Fig. 5c travel col linearly instead of antiparallel a particular situation arises. The simultaneous interaction of both waves with the molecule may be regarded as a resonant stimulated Raman scattering process. It can be shown39 that in such a case the width yqr of the double resonance signal is given by... 

Here we extend the simple three-level EIT system to mote complicated and versatile configurations in a multi-level atomic system coupled by multiple laser fields. We show that with multiple excitation paths provided by different laser fields, phase-dependent quantum interference is induced either constractive or destractive interfereiKe can be realized by varying the relative phases among the laser fields. Two specific examples are discussed. One is a three-level system coupled by bichromatic coupling and probe fields, in which the phase dependent interference between the resonant two-photon Raman transitions can be initiated and controlled. Another is a four-level system coupled by two coupling fields and two probe fields, in which a double-EIT confignration is created by the phase-dependent interference between three-photon and one-photon excitation processes. We analyze the coherently coupled multi-level atomic system and discuss the control parameters for the onset of constructive or destructive quantum interference. We describe two experiments performed with cold Rb atoms that can be approximately treated as the coherently coupled three-level and four-level atomic systems respectively. The experimental results show the phase-dependent quantum coherence and interference in the multi-level Rb atomic system, and agree with the theoretical calculations based on the coherently coupled three-level or four-level model system. 

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