Observation of quasilinear fluorescence spectra (the "Shpol'skii effect") in matrix-isolated polycyclic aromatic hydrocarbons

Abstract

1769boundary and depend on its structure (we neglect any proton transfer in the interior of the micelles having low dielectric constant, since ten units lowering of it than water was observed to lower the complexation significantly under the present experimental conditions*). The ASo values given in Table I varied in the order SDS < water < T X 100 < (CTAB + TX 100) < (SDS + T X 100) < CTAB < PEG. The environment for the reaction was then most ordered in SDS, much less in CTAB, and the least in PEG.The free energy changes for the individual additives followed the order PEG < T X 100 < water < SDS < CTAB. Appearance of PEG and CTAB at the two extreme ends and that of SDS just before CTAB advocated the significant roles of charge and other specific effeds1i4 than the water structure. The effects of micellar charge, the environmental dielectric, changed pK, water structure, and the partition of the species between the micelle and the bulk would all work in conjunction, whose dissection at present would not be meaningful.In conclusion we make a statement that inspite of accepting the error related possibility of a linear enthalpy-entropy correlation,21 we observed such a nice extrathermodynamic compensation for the present proton transfer process in the presence and absence of different additives including the hydroxylic nonaqueous solvents reported earlier.4 Publication costs assisted by the National Science Foundation and the Nectric Power Research InstituteQuasilinear "Shpol'skii" fluorescence spectra of polycyclic aromatic hydrocarbons can be observed by matrix isolation, employing an n-alkane as the matrix, if the vapor-deposited sample is annealed at elevated temperature (ca. 140 K) prior to observation of the spectrum at low temperature (16 K). Quasilinear spectra obtained by matrix isolation compare closely to those obtained by conventional frozen-solution techniques in Shpol'skii matrices. Temperature variations of vapor-deposited samples after deposition but before spectral measurements reveal the presence of matrix "memory effects".

Quasi-line Spectral Emissions from Highly Crystalline One-Dimensional Organic Nanowires

“…At cryogenic temperatures, further freezing of the molecular degrees of freedom and the reduction of thermal phononic coupling result in quasi-line spectra 33 from PEN wires. This emergence of these atomic-like quasi-line spectra is called the Shpol'skii effect 13,34 and was reported in frozen organic solutions at low temperatures by Shpol'skii in 1952. The reported quasi-line spectra have a line width of ∼1 to 2 nm and are a result of the reduced phononic coupling with the excitons in the lattice.…”

Determination of polycyclic aromatic hydrocarbons in unfractionated solid solvent-refined coal by matrix isolation fluorescence spectrometry

“…Samples were codeposited by vacuum sublimation with matrix gas as described previously (17). Upon completion of deposition, samples in n-heptane and n-octane matrices were annealed (23) at 150 K and 155 K, respectively, for 5 min before viewing spectra at 15 K. Matrix solvents including "distilled in glass" n-heptane (Burdick and Jackson) and 99.8% (GC) n-octane (Tridom Chemical, Inc.) were used as received. The total time required for the complete deposition procedure (cool-down, deposition, and annealing) was typically 2 h.…”

Characterization of Coal-Derived Materials by Matrix Isolation Spectroscopy

“…The characteristics of MI fluorescence spectra of PAHs and their derivatives have been discussed in a series of publications from this laboratory (1, [11][12][13][14][15][16][17][18][19] ; the following characteristics of MI fluorescence spectrometry are especially relevant to PAH analyses in coal-derived materials. First, highly resolved spectra are obtained* Sufficient for distinguishing between isomeric PAHs, such as the six isomeric methylchrysenes (12).…”