Electronic Structure and Spectral-Fluorescent Properties of Thiopyrylo-4-Tricarbocyanine Laser Dyes

Optics and Spectroscopy - We found that the long-wavelength absorption band of the laser dye IR 1061 and its analogue with an unsubstituted polymethine chain is strongly broadened and decreases in...     

Heterospin complexes of polynuclear Ni<Superscript>II</Superscript> compounds containing hexafluoroacetylacetonate and pivalate ligands with nitroxides

The heterospin mixed-ligand complex [Ni₆(OH)₄Piv₄(hfac)₄(NIT-Ph)₂] (1) (NIT-Ph is 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, hfac is hexafluoroacetylacetonate, and Piv is pivalate) was synthesized. The method for the synthesis of complex 1 is based on the replacement of acetone molecules in the hexanuclear complex containing the hexafluoroacetylacetonate and pivalate ligands [Ni₆(OH)₄Piv₄(hfac)₄(Me₂CO)₄] by NIT-Ph molecules. Two monodentate NIT-Ph molecules replace four acetone molecules, because the coordination of the O atom of the nitroxide group results in the blocking of one of the positions in the coordination environment of Ni^II the access to which is hindered by the phenyl ring of NIT-Ph. As a result, these ions are in a square-pyramidal environment unusual of Ni^II. In the low-temperature range, the dependence of the magnetization of 1 on the magnetic field is described by the Brillouin function. The reaction of [Ni₆Piv₄(hfac)₄(OH)₄(Me₂CO)₄] with the nitronyl nitroxide radicals 4,4,5,5-tetramethyl-2-(4-pyridyl)-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (NIT-p-Py) or 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (NIT-Iz) containing the pyridine or 1-methylimidazol-5-yl substituent, respectively, in the side chain is accompanied by the decomposition of the polynuclear fragment and affords the mononuclear complexes Ni(hfac)₂(NIT-p-Py)₂ and Ni(hfac)₂(NIT-Iz)₂, respectively. The reaction of 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihyd-ro-1H-imidazol-1-oxyl (Im-Iz), which is the imine analog of NIT-Iz, with [Ni₆Piv₄(hfac)₄(OH)₄(Me₂CO)₄] afforded the decanuclear complex [Ni₁₀(OH)₈Piv₄(hfac)₈(Im-Iz)₂(H₂O)₆]. The molecular and crystal structures of all heterospin compounds were determined, and the magnetic properties of all compounds were investigated in the 2–300 K temperature range.     

On solvability of some special systems of one-dimensional loaded parabolic equations and composite-type systems with Cauchy data

We study a one-dimensional system of two parabolic loaded equations of a special kind and a one-dimensional composite-type system of a special kind. Both systems are considered with Cauchy data. We obtain sufficient conditions for the existence of a solution in the class of bounded smooth functions. The method of splitting on the differential level (the weak approximation method) is used in the proof.     

Substituent and Solvent Effects on The Electronic Absorption Spectra of Phosphapyrimidine Derivatives

U.v spectra study of phosphacgclic compounds with tetracoordinated ring phosphorus atom has been an object of a rather limited number of WOZkS. There are only few works on U.V. absorption spectra of cyclic phosphonitriles which reveal a specifio character of their Π-electronic structure¹; besides, there are some data on a significant low - frequency shifting of the electronic spectrum of 1.1 - diphenylphos-phabemene against that of benzene². This communication presents an analyisis of the experimental findings on electronic absorption spectra of a Wide variety of substituted phospha-pyrimidines, PhP, (1,2,6 - phosphadiazines) for elucidating the nature of the observed absorption ban and for studying electronic distribution as well as separate characteristics of the php moLecules in the ground and excited states.     

Coherent momentum transfer due to interaction between three-level atoms and counterpropagating laser pulses

A theoretical analysis is presented of the change in the momentum of a three-level atom due to its interaction with counterpropagating laser pulses that overlap in time. The two lower energy states of the atom are metastable; i.e., a lambda-type configuration of atomic levels is considered. The cases of two and four counterpropagating pulses having different carrier frequencies are considered. In the case of adiabatic atom-field interaction, it is shown that the atom’s momentum can change by an integer multiple of the photon momentum and the corresponding standard deviation is small as compared to the photon momentum squared.