Therefore, already the Coulomb interaction among P _ \ mathbf { k } produces a new solid-state effect compared with optical transitions in simple atoms.
12.
To predict the optical transition with appropriate precision, one chooses an approximation, called the assumption of quasi-thermal distributions, of the electrons in the conduction band and of the holes in the valence band.
13.
*The dynamics is quite different for high energies, such as occur from an optical transition from a non-degenerate initial state with a high-symmetry ( JT undistorted ) equilibrium geometry into a JT distorted state.
14.
Due to this coupling among the excitations for all values of the crystal momentum \ hbar { \ mathbf k }, the optical excitations in semiconductor cannot be described on the level of isolated optical transitions but have to be treated as an interacting many-body quantum system.
15.
On first sight, it may seem strange to treat optical transitions of a collisional complex, which may exist just momentarily, for the duration of a fly-by encounter ( roughly 10 " 13 seconds ), in much the same way as this was long done for molecules in ordinary spectroscopy.
16.
His method of calculating the optical response of a crystal based on pseudopotentials for electronic band structure and on the analysis of symmetry at the critical point is developed in one of his most significant publications, " Electronic States and Optical Transitions in Solids " ( with G . Pastori Parravicini, Pergamon Press, Oxford 1975 ).
17.
The amplitude of soliton pulses is so high that the electron states in a quantum well make temporal excursions in energy up to 10 meV . The subpicosecond duration of the solitons is less than the coherence time of the optical transition between the electron states and a frequency modulation of emitted light during the coherence time ( chirping effect ) is observed.
18.
These include ( but are not limited to ) Beam Position Monitors ( BPMs ) to measure the position of the bunch, screens ( fluorescent screens, Optical Transition Radiation ( OTR ) devices ) to image the profile of the bunch, wire-scanners to measure its cross-section, and toroids or ICTs to measure the bunch charge ( i . e ., the number of particles per bunch ).
19.
Both ordinary and collision-induced spectra may be observed in emission and absorption and require an electric or magnetic multipole moment-in most cases an electric dipole moment-to exist for an optical transition to take place from an initial to a final quantum state of a molecule or a molecular complex . ( For brevity of expression we will use here the term " molecule " interchangeably for atoms as well as molecules ).
