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Ultrafast phenomena: Experimental
Published in Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George, Introduction to Ultrafast Phenomena from Femtosecond Magnetism to high-harmonic Generation, 2020
Guo-ping Zhang, Georg Lefkidis, Mitsuko Murakami, Wolfgang Hübner, Tomas F. George
If we Fourier-transform the time evolution of the transmittance change, we can detect the frequency change due to the photoisomerization. These frequency changes can be correlated to the molecular motion. For the symmetric double bond C = C and C = N stretching modes, their frequency is in the wavenumber range 1500-1550 cm−1. We can convert wavenumbers to eV using E = hc/λ, where h is the Planck constant, c is the speed of light, and λ is the wavelength. Recall from Chapter 1 that the wavenumber is simply the inverse of the wavelength, 1/λ, but the wavelength must be expressed in the unit of length (cm). 1 eV is equal to 8065.6 cm−1, so the above wavenumber is about 0.19 eV, which is very high for a molecular vibration. For the in-plane C = C – H bending, the wavenumber is 1150-1250 cm−1, lower than the above. The hydrogen out-of-plane mode has a wavenumber at 900-1000 cm−1. This mode is associated with the C13-C14 bond, so it can signal whether the isomerization really occurs or not. Therefore, its appearance is of central importance to photoiso-merization. Ultrafast lasers are capable of detecting when this occurs. This frequency only appears within 300 fs.
Techniques
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
The horizontal axis of a Raman spectrogram shows a wavenumber scale. Wavenumber is the number of waves per distance (centimeter), rather than the number of waves per time (second). In other words, frequency is the number of waves that pass by a fixed point in one second. Wavenumber is the number of waves in one centimeter. The unit may be described as “wavenumber/cm,” which is the same as “wavenumber cm−1.”
Magnetic Field Effects on Wave Propagation Characteristics of Smart Nanostructures
Published in Farzad Ebrahimi, Ali Dabbagh, Wave Propagation Analysis of Smart Nanostructures, 2019
Furthermore, the effect of the applied Lorentz force on the phase velocity of the scattered waves is again studied in Figure 11.7 for various wave numbers and gradient indices. In fact, due to the decreasing impact of gradient index on the equivalent stiffness of the implemented FGM (i.e., the total stiffness will be closer to that of the ceramic-rich phase with increase the gradient index), the phase velocity becomes smaller once a greater value is assigned to the gradient index. In addition, increasing the wave number results in achieving greater phase speeds. However, the slope of enhancement of phase speed with increment of magnetic field intensity becomes smaller as the wave number is added. It is worth mentioning that the enhancement of the dynamic response of the continuous system occurs with a nonlinear profile. Hence, former estimations can also be observed in this diagram (Figure11.8a).
Guided wave propagation of porous functionally graded plates: The effect of thermal loadings
Published in Journal of Thermal Stresses, 2021
In Figures 3 and 4, we respectively studied the influence of temperature load on phase velocity and group velocity, both the UTR and N-UTR case are studied. It can be seen from Figures 3 and 4 that the phase velocity seems to be a decreasing function of wave number, that is, with the increase of wave number, phase velocity decreases; On the contrary, for group velocity, the phase velocity seems to be an increasing function of wave number. In other words, with the increase of wave number, the group velocity decreases. Obviously, wave number has different effects on phase velocity and group velocity. In addition, we can also find that for both phase velocity and group velocity, once the temperature rises, the phase velocity and group velocity will decrease. Moreover, we can see that UTR has more significant effect on phase velocity and group velocity than N-TUR for the same temperature changes.
Experimental study of roughness spectrum of sandy seafloor with an underwater laser 3D scanning system
Published in Marine Georesources & Geotechnology, 2023
Guangming Kan, Jingqiang Wang, Xiangmei Meng, Zhiguo Yang, Shengqi Yu, Guanbao Li, Baohua Liu, Pengyao Zhi
It shows that the wavenumber is inversely proportional to the wavelength. If the roughness spectrum is normalized, then the integration of the wavenumber over the entire range of Kx and Ky (including positive and negative values) is equal to the mean square roughness h2