Linewidth narrowing

One of the potentially most interesting aspects of the resonant collisions is that, in theory, the collision time increases and the linewidth narrows as the collision velocity is decreased. According to Eqs. (14.6) and (14.8) the collision time is proportional to l/v3/2. Collisions between thermal atoms with temperatures of 500 K lead to linewidths of the collisional resonances that are a few hundred MHz at n = 20. In principle, substantially smaller linewidths can be observed if the collision velocity is reduced. 

Overwhelmingly, the published research on Raman-based biofluid analysis uses excitation in the near-infrared regime in order to reduce fluorescence. Standard linewidth-narrowed diode lasers at 785 or 830 nm are most common. As noted in Chap. 1, several hundred milliwatts of multiple-spatial mode light can routinely be obtained from diode lasers, making them economical choices... 

Paspalakis and Knight [28] have considered a V-type three-level system driven from an auxiliary level by two laser fields of the same frequencies. They have predicted linewidth narrowing and cancellation of the fluorescenc, which can be controlled via the phase difference between the two laser fields used for the excitation. Ghafoor et al. [29] have considered a four-level system in which quantum interference can be generated by three driving fields and have shown that the linewidths and intensities of the spectral lines can be controlled by the phases and amplitudes of the driving fields. 

The bond dissociation energy of C—G is about 20kcal/mol smaller than that of a C—H bond. Therefore structure (C) is the most probable. The linewidth narrowing by heat treatment observed here seems to be... 

Saito(S). Comments on Br NMR linewidth narrowing in 79/8iBr-203/205xi double-resonance experiments ... 

Detailed information on structure and dynamics is also available for cyclopentane. Proton NMR studies show in this case coincidence of the linewidth narrowing from a second moment of 26.2 1.5 G expected for a rigid crystal (calculated 28 + 2 G ) with a sharp thermodynamic transition at T, = 122.4 K. The re-... 

Good evidence for the rapid motion and trapping of the soliton is demonstrated by a DNP experiment as shown in Figure 6.30 [146,173]. The dynamic nuclear polarization (DNP) experiments are carried out at 9 GHz between 1.5 and 300 K in cis [143,174] and irons PA [143,145,146,173,174]. At room temperature the pure Overhauser effect (OE) was observed in a -irans-PA without air or oxygen but a mixed solid state effect (SSE) together with OE was found in c/s-rich PA without air [143,174] and al -lrans-PA with air [146]. In particular, below 150 K, the mixed effect was observed, even in a -trans-PA without air [145,173], The OE is characteristic of dynamic interaction between nuclear spins and electron spins, with rapid motion, On the other hand, the SSE is of the static interaction between them. In other words, observation of the pure OE is clear evidence for the electron spin for motion with an inverse of the correlation time comparable with or larger than Wj,. At 300 K, the pure OE observed in all-/ra s-PA, is consistent with the conclusions for the neutral soliton to diffuse rapidly compared with 1/We as concluded from the ESR linewidth narrowed by motion [53] and the proton NMR 7Y ] [143] as a function of frequency over a broad range. 

The Chapter is organized as follows. First the theoretical calculations with A -type three-level atoms in the optical ring cavity are described. The EIT-enhanced linear and nonlinear dispersions are calculated, and their effects to the cavity linewidth are discussed in different parametric regions. Second, various experimental observations are presented to demonstrate those interesting effects on cavity linewidth narrowing and broadening, as well as WLC. The last part serves as the summary with some discussions. 

Wang H, Goorskey D, Burkett WH and et al. Cavity-linewidth narrowing by means of electromagnetieally indueed transparency. Optics Letters 2000 Dec 1 25(23) 1732-1734. 

Li YH, Jiang HT, He L and et al. Linewidth narrowing in microstrip resonator using effective highly dispersive medium. Chinese Physics Letters 2007 Apr 24(4) 975-978. 

Wu H and Xiao M. Cavity linewidth narrowing and broadening due to competing linear and nonlinear dispersions. Optics Letters 2007 Nov 1 32(21) 3122-3124. 

Figure 4 shows a plot of the lineshape ( >). If one identifies l/twm with the deterministic equivalent of z, it is seen that the linewidth narrowing of Figs. 3b and 4 and is quite the same effect. 

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