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What Is the Stimulated Emission of Radiation?
Published in Travis S. Taylor, Introduction to Laser Science and Engineering, 2019
Figure 3.7 shows a system in the doublet state. For a system to be in the doublet state the sum of the spins of the quantum system must equal ½. Figure 3.8 shows a system in the triplet state. The figure on the left side of Figure 3.8 shows the case of a spin flip within the same shell and on the right side shows an excitation to the next level. For the electron to drop back to the ground singlet state it should emit a photon. This process is called phosphorescence. It will be important later to note that fluorescence usually occurs many orders of magnitude faster than phosphorescence.
A selective NO sensor based on the semiconducting BC2N nanotubes: a computational study
Published in Molecular Physics, 2020
Yongqiu Liu, Chao Liu, Ajit Kumar
We have accomplished all computations by applying the software of GAMESS [41]. For picturing density of state (DOS) diagrams, GaussSum package was applied [42]. Optimizations of all structures and nuclear magnetic resonance (NMR) [43], energetic, and electronic analyses were completed using the B3LYP-gCP-D3/6-31G* model chemistry. The dispersion interaction estimation is the weakness of the traditional DFT functionals such as B3LYP which has been regularly used for different purposes [44]. The B3LYP-gCP-D3 [45] has the B3LYP advantages, and also estimates the weak London interactions, correcting the basis set superposition errors (BSSE). For the computation of interaction energy (InE) of gas molecules on the BC2NN, the below formula was applied: where E (BC2NN) is the BC2NN energy. E (gas/BC2NN) is the energy of each BC2NN with CO or NO molecule attached to its surface. All structures are neutral with zero global charge. Spin multiplicity is 2 (doublet state) for open shell systems which include odd number of NO molecules and that is 1 (singlet state) for closed shell systems. The all of calculated vibrational frequencies are positive, confirming that the structures are true local minima.