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91.
Singh PN Mandel SM Robinson RM Zhu Z Franz R Ault BS Gudmundsdóttir AD 《The Journal of organic chemistry》2003,68(21):7951-7960
We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis of alpha-azido acetophenone derivatives, 1. Alphazides 1 contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1 cleave to form benzoyl and methyl azide radicals in competition with triplet energy transfer to form triplet alkyl nitrene. The major photoproduct 3 arises from interception of the triplet alkyl nitrene with benzoyl radicals. The triplet alkyl nitrene intermediates are also trapped with molecular oxygen to yield the corresponding 2-nitrophenylethanone. Laser flash photolysis of 1 reveals that the triplet alkyl nitrenes have absorption around 300 nm. The triplet alkyl nitrenes were further characterized by obtaining their UV and IR spectra in argon matrices. (13)C and (15)N isotope labeling studies allowed us to characterize the C-N stretch of the nitrene intermediate at 1201 cm(-)(1). 相似文献
92.
New Benzyl Complexes of the Lanthanides. Synthesis and Crystal Structures of [(C5Me5)2Y(CH2C6H5)(thf)], [(C5Me5)2Sm(CH2C6H5)2K(thf)2]∞, and [(C5Me5)Gd(CH2C6H5)2(thf)] YBr3 reacts with potassium benzyl and [K(C5Me5)] in THF to give KBr and the monobenzyl compound [(C5Me5)2 · Y(CH2C6H5)(thf)] 1 . The analogous reaction with SmBr3 in THF leads to the polymeric product [(C5Me5)2Sm(CH2C6H5)2 ∞ K(thf)2]∞ 2 , with GdBr3 to [(C5Me5)Gd(CH2C6H5)2(thf)] 3 . The structures of 1–3 were determined by X-ray single crystal structure analysis:
- Space group P1 , Z = 2, a = 851.2(4) pm, b = 952.7(4) pm, c = 1858.6(8) pm, α = 79.90(4)°, β = 77.35(4)°, γ = 73.30(3)°.
- Space group P1 , Z = 2, a = 903.3(2) pm, b = 1375.9(3) pm, c = 1801.1(4) pm, α = 100.92(3)°, β = 100.77°, γ = 98.25(3)°.
- Space group P21/n, Z = 8, a = 1458.2(5) pm, b = 927.8(3) pm, c = 3792.9(15) pm, β = 96.83(3)°.
93.
R. N. Shakhmuratov J. Odeurs S. Gheysen Y. Rostovtsev O. Kocharovskaya P. Mandel 《Laser Physics》2007,17(5):716-719
We discuss level mixing induced transparency (LMIT), which is experimentally found in a thick absorber of FeCO3 containing the 57Fe Mössbauer nuclei. LMIT is observed if two hyperfine levels of the excited state nucleus cross. Absorption of gamma radiation drops by about 25% with respect to the sum of two overlapping absorption lines. The absorption deficit is explained by the mixing of the crossing levels with a symmetry breaking interaction. The level mixing induces a polarization change of the scattered radiation. In such a way, the radiation develops in “normal modes,” which are less absorbed in a thick absorber. We show that, in spite of the absorption drop, the area of the absorption line does not change. This confirms the general knowledge that interference phenomena (destructive or constructive) do not change the lifetime of an excited state particle (atom, nucleus, etc). 相似文献
94.
We show that coupling diffraction and chromatic dispersion lead to body-centered cubic and hexagonally packed cylinders of dissipative optical crystals in a degenerate optical parametric oscillator. The stabilization of these crystals is a direct consequence of the interaction between the modulational and the quasi-neutral modes. 相似文献
95.
Synchronization due to a weak global coupling with time delay in a semiconductor laser array is investigated both in the cw and self-pulsing regimes. A generalized form of the Kuramoto phase equations is derived and discussed analytically. The time delay is shown to induce in-phase synchronization in all dynamical regimes. Another form of synchronization is found which leads to local extinction of self-pulsing in the array. 相似文献
96.
We study the dynamics of the formation of circular domain walls, which are large-intensity structures, in a degenerate optical parametric oscillator. We show that the mean-field and the propagation models predict the same increase in the domain size proportional to t(1/3) . 相似文献
97.
L. Mandel 《Physics letters. A》1982,89(7):325-326
Some difficulties with a modified version of the Pfleegor-Mandel experiment recently proposed by Garuccio, Popper and Vigier are pointed out, and a different modification is proposed in order to test the conventional quantum mechanical interpretation. 相似文献
98.
T. Mandel G. Kaindl K. Horn M. Iwan H.U. Middelmann C. Mariani 《Solid State Communications》1983,46(9):713-716
Photoelectron spectra of the krypton 3d core-levels and MNN Auger spectra of krypton mono- and multilayers on Cu(110) have been recorded with synchrotron radiation. The Kr-3d line is found to shift to higher binding energies by 0.73 eV for first- and second-layer adsorption, respectively. This value is much larger than the work function decrease for Kr mono-layer adsorption, Δø = ?0.29eV. The shift in Auger line energies is found to be about three times larger than the 3d line shift. These observations can be readily explained in terms of image-charge screening of the hole states. 相似文献
99.
100.
We study the mean field properties of a solid-state monomode laser containing a saturable absorber which can undergo only two-photon transitions. Even when the cavity is tuned to the atomic line center there are two classes of stationary solutions, one of which is tuned to the microscopic frequency whereas the other one is always detuned. Furthermore optical bistability arises either between two tuned states or between a tuned and a detuned state. 相似文献