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Microwaves
Published in Mario Bertolotti, The History of the Laser, 2004
The interaction of microwaves with matter may produce transitions between energetic levels of molecules that, being very near one to the other, correspond to the low energy carried by the microwave photons. Microwaves may also interact with the magnetic moment of the electron (spin) or of the nuclei. In these cases the magnetic field of the waves interacts with the magnetic moment of the particle (electron or nucleus) and orients it by exchanging energy. These phenomena of interaction between microwaves and matter are the object of microwave spectroscopy. Microwave spectroscopy was born naturally from the development, during the Second World War, of radar and microwave oscillators. After the war these oscillators were used for spectroscopic studies that allowed the smaller details of the molecular structure and of the atomic nuclei to be measured. The only measurement performed before the war with microwaves was that of the inversion frequency of ammonia in the centimetre region performed by Cleeton and Williams in 1934, of which we have already spoken.
Why Microwaves?
Published in Iain H. Woodhouse, Introduction to Microwave Remote Sensing, 2006
A unique feature of microwave spectroscopy for radiometry is the ability to design instrumentation which simultaneously gives the best possible spectral resolution and sensitivity of thermal emission measurements at long wavelengths. Measurements can be made of a number of physical parameters and molecular concentrations required for monitoring the global atmospheric system and for testing and developing atmospheric models; e.g. temperature, pressure, liquid water, rainfall, and a collection of molecular concentrations, including water vapour and ozone.
Nonlinear optical properties of coupled quantum dots in peanut configuration
Published in Philosophical Magazine, 2023
E. S. Hakobyan, D. A. Baghdasaryan, E. M. Kazaryan, P. A. Mantashyan, D. B. Hayrapetyan
Different growth techniques made it possible to grow QDs of various shapes and sizes, for example, spherical [23], ellipsoidal [24], pyramidal [25,26], cylindrical [27–30], conical [31,32] and lens-shaped [33–35]. QDs have been extensively fabricated and investigated both theoretically and experimentally. It is worth noting that spheroidal and ellipsoidal or other specific shaped QDs offer an advantage over spherical ones, as they possess additional geometrical parameters that can be tuned to achieve desirable optical properties. On the other hands, analogous to real atoms, two or more QDs can form a molecule-like structure, commonly referred to as a QDs molecule. In addition to growing QDs of specific shapes, the self-assembly of two or more individual QDs can result in groups that are interconnected, forming unique structures. In article [36], the authors present research that utilises microwave spectroscopy to study the properties and behaviour of QDs molecule. They propose a theoretical model that allows for the examination of the electronic properties of such structures. Moreover, it is shown that QDs molecules are structurally and electronically linked [37]. Coherent coupling and hybridisation of the wave function appear in the redshift of the band gap, which is consistent with quantum mechanical simulations. Spectroscopy of single nanoparticles revealed the properties of bound nanocrystals, particularly quantum mechanical tunnelling and energy transfer.
Dimers and trimers of HF, H2O, NH3 and CH4 with N2. Ab initio studies on structures and vibrational frequencies
Published in Molecular Physics, 2021
As shown in Ref. [13], two structures of the NH3-N2 complex, labelled 1Ln (Fig. S8 in Supplement) and 2Ln (Fig. S9 in Supplement) have nearly the same energy, 245 and 246 cm−1, respectively, obtained with the CCSD(T) method. 1Ln has a strongly bent N1-H2-N6 hydrogen bond, whereas 2Ln is not hydrogen bonded, having N2 close to N of NH3. A 2Ln-type structure has been predicted by microwave spectroscopy [7–10]. A recent theoretical result by Surin et al. [11] of De=250.6 cm−1 is in good agreement with the present result. The MP2 dissociation energies for the 1Ln and 2Ln structures of NH3-N2 are almost 30 cm−1 higher than the corresponding CCSD(T) values, a rather large difference, despite their optimised structures being very similar. Both the 1Ln and 2Ln structures have no imaginary frequencies.
Laser spectroscopy of 176Lu+
Published in Journal of Modern Optics, 2018
R. Kaewuam, A. Roy, T. R. Tan, K. J. Arnold, M. D. Barrett
Frequency references for transitions are denoted , where F denotes the hyperfine level of . These frequencies are determined by a combination of optical and microwave spectroscopy. Optical spectroscopy starts with driving clock transitions from to . After Doppler cooling, the ion is optically pumped to . A interrogation pulse then drives the atom down to either which is followed by detection. Using the technique discussed in [7], the clock laser is servoed to both Zeeman states to stabilize the laser frequency to the centre of the ground-state Zeeman spectrum. Referencing the laser to the frequency comb gives