Spectra phosphorescence

Phosphorescence Spectra.—Luminescence from a low-lying triplet state of water368 has been reported. It has been shown that two long-lived emission systems in the biacetyl crystal described previously by Sidman and McClure (see ref. 368) are in fact due to impurities, and a complete analysis is presented of the true 3AU xAg phosphorescence. The zero-zero band in emission is found at 20 327 cm-1.135 A satisfactory account of the six characteristic bands in the phosphorescence spectrum of benzene has been given on the basis of pseudo-Jahn-Teller vibronic interactions between the lower 3Blu and 3Elu states in which two active vibrations in the pseudo-cylindrical approximation are considered.369 The phosphorescence spectra of anthracene,3700 coronene,8706 benzophenone in aqueous solution,371 pyrimidine derivatives,372 porphyrins,298 873 and crystalline charge-transfer complexes 374 have been reported. 

Tribophosphorescence in aniline hydrochloride and coumarin 376 and recombination luminescence in benzene and L-tryptophan 376 have also been discussed, and some chemiluminescence spectra of CN, SrO, and FeO presented.377 

Double-resonance Spectroscopy.—A review has been given of double-resonance methods in spectroscopy.378 Attention will be focused here on optically (usually phosphorescence) detected magnetic resonance experiments (ODMR). Microwave-optical double-resonance experiments have been carried out on the spectrum of gaseous N02,379 permitting assignment of the rotational = 0—4 side-bands of the 493 nm band. 

Studies have been carried out using ODMR methods on the lowest triplet state of toluene,380 / -chloroaniline,381 and dibromonaphthalene single crystals.382 344 

Mohwald and E. Sackmann, Chem. Phys. Letters, 1974,26,509 T. Amano and Y. Kanda, Bull. Chem. Soc. Japan, 1974,47,1326 A. Ponte-Goncalves and R. J. Hutton, J. Phys. Chem., 1975, 79, 71. 

PHOSPHORESCENCE SPECTRA In addition to fluorescence emission bands, some of these compounds may show phosphorescence emission bands which are on the long wave length side of the fluorescence spectra. Calvin and Dorough (16a) have shown that zinc chlorin, and a mixture of chlorophylls a plus b, possess phosphorescence bands beginning in the range of 7800 to 8000 A and extending into the infrared. The lifetime of the phosphorescent state was about 0.2 second. Copper chlorin, which does not show fluorescence, also does not show phosphorescence. 

TABLE 1-19. ULTRAVIOLET ABSORPTION SPECTRA OF THIAZOLIUM TOSYLATES IN EtOH (186) COMPARED WITH CALCULATED TRANSITION ENERGIES (187) 

A schematic diagram of a high-resolution luminescence spectrometer for research purposes, recently described by Vo Dinh et al. , is shown in Fig. 24. 

For operational purposes, fluorescence is understood to be short-lived and phosphorescence to be long-lived luminescence. The spectrometer described here uses only a single light chopper 9 and allows simultaneous recording of total luminescence and phosphorescence spectra (Fig. 25). 

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Fluorescence and phosphorescence spectra of poly(propynoic acid)(FPA), polyphenylene (PP), and DPAcN show that the difference of energies between the lower excited singlet and triplet states, as observed in the case of PP (583 nm) and DPAcN (528 nm), is considerably greater than that of poly(propynoic acid) (270—300 nm) which besides transitions may undergo rr - transitions. PCSs showing only... 

In 1944, Lewis and Kasha (52) identified phosphorescence as a forbidden" transition from an excited triplet state to the ground singlet state and suggested the use of phosphorescence spectra to identify molecules. Since then, phosphorimetry has developed into a popular method of analysis that, when compared with fluorometry, is more sensitive for some organic molecules and often provides complimentary information about structure, reactivity, and environmental conditions (53). 

Burrell and Hurtubise (.32) investigated calibration curves extended well beyond the normal linear range for RTF and RTF of benzoCf)quino-line adsorbed on a silica gel chromatoplate under neutral and acidic conditions. As the benzoCf)quinoline concentration increased, the RTF curves leveled off, whereas the RTF curves passed through a maximum and then decreased. The extended calibration curves along with fluorescence and phosphorescence spectra and phosphorescence lifetimes for benzoCf)quinoline revealed differences in the RTF and RTF phenomena. For example, it was determined that RTF could arise from molecules adsorbed on the surface and in multilayers of molecules, whereas phosphorescence was only generated from molecules adsorbed on the surface of the chromatoplate and not in the multilayers. ... 

Generally in solution at room temperature only fluorescence emission is observed. To obtain phosphorescence spectra, low temperatures are used and a rotating can with a narrow slit in the side is placed around the sample. Since the lifetime of the fluorescent state is generally much shorter than that of the phosphorescent state, the time required for the slit in the can to rotate 90° ensures that only the longer lived phosphorescence will be observed. 

Fluorescence and phosphorescence spectra corrected for the instrumental sensitivity were measured with a spectrometer described previously (()). Corrected excitation spectra were obtained with constant excitation intensity controlled by a rhodamine B quantum counter. For phosphorescence polarization measurements the apparatus was set up in an "In Line" arrangement (j ) and equipped with a Glan-Thomson polarizer and a sheet polarizer (analyser) (10). 

Photophysical Processes in Dimethyl 4,4 -Biphenyldicarboxy-late (4,4I-BPDC). The ultraviolet absorption spectrum of dimethyl 4,4 -biphenyldicarboxyl ate was examined in both HFIP and 95% ethanol. In each case two distinct absorption maxima were recorded, an intense absorption near 200 nm and a slightly less intense absorption near 280 nm. The corrected fluorescence excitation and emission spectra of 4,4 -BPDC in HFIP at 298°K shows a single broad excitation band centered at 280 nm with a corresponding broad structureless emission band centered at 340 nm. At 77°K, the uncorrected phosphorescence spectra shows a single broad structureless excitation band centered at 298 nm, and a structured emission band having maxima at 472 and 505 nm with a lifetime, t, equal to 1.2 seconds. 

Figure 6). The phosphorescence spectra of the copolymer yarns showed excitation in the 305 - 310 nm range with corresponding emission maxima at 480 and about 515 nm, corresponding lifetimes equal 1.2 seconds. In the copolymer yarns containing 0.5 - 2.0 mole percent 4,4 -BPDC a small shoulder was observed at 452 corresponding to the PET homopolymer phosphorescence. 

In the yarns, the fluorescence of the 4,4 -biphenyldicarboxy-late unit is distinct and predominate both at 298 and 77°K. Examination of the phosphorescence spectra of the PET and PET-co-4,41-BPDC yarns revealed three emission maxima. In the PET homopolymer excitation with 310 nm radiation produced an emission at 452 nm from the terephthalate chromophore. In the copolymers excitation with either 305 or 310 nm radiation produced emission spectra with distinct maxima at 480 and 515 nm (t 1.2 sec), and a shoulder near 452 nm (t = 1.2 sec). The maxima in the phosphorescence spectra were assigned as emission from the 4,4 -biphenyldicarboxylate units of the copolymer. The observed emissions are bathochromatically shifted from the emission of 4,4 -BPDC in a glassed solvent. This is supported by the observed emissions from solid 4,4 -BPDC at 520 and 560 nm (t =. 3 sec) when excited with 340 or 356 nm radiation. 

The phosphorescence characteristics of the copolymer yarns are somewhat unexpected. It has been shown previously that the terephthalate emission should predominate in the phosphorescence spectra. It has also been shown previously that in mixed... 

Figure 6. Uncorrected phosphorescence spectra of poly(ethylene terephthalate)...

Photophysical Processes in Pi butyl 4,4 -Sulfonyldibenzoate (4,4 -SD). The UV absorption spectra of dibutyl 4,4 -sulfonyl-dibenzoate (4,4 -SD) in both HFIP and 95% ethanol showed similar absorptions. The corrected excitation and emission fluorescence spectra of 4,4 -SD in HFIP at 298°K showed a structured excitation with band maxima at 236, 286, and 294 nm and a structured emission exhibiting band maxima at 322, 372, and 388 nm. The uncorrected excitation and phosphorescence spectra of 4,4 -SD in a 95% ethanol glass at 77°K displayed excitation band maxima at 268, 282, and 292 nm with strong phosphorescence emission with band maxima at 382, 398, and 408 nm with a mean lifetime (t) of 1.2 sec. 

The 0-0 transition bands exhibited in the fluorescence and phosphorescence spectra of 4,4 -SD gave the following electronic state energies Sj 33,000 cm-1, Sg 42,000, and ... 

Since the solution and yarn fluorescence and the phosphorescence spectra give no indication of the presence of the comonomer, 4,4 -SD, we conclude that the comonomer excitation and emission are hidden under the strong excitation and emission bands of the dominant PET absorbing species and that a coabsorption, co-emission process is probably occurring. 

Analyses I.r. spectra were measured as smears on sodium chloride plates or as a solution in carbon tetrachloride using a Perkin-Elmer 567 grating spectrophotometer, while u.v. spectra were measured as a solution in hexane (spectroscopic grade) using a Unicam SP 1700 instrument. Fluorescence and phosphorescence spectra were recorded as described elsewhere (5, 6). 

Tomin VI, Rubinov AN, Kozma L (1973) Inhomogeneous broadening of a and P phosphorescence spectra of dyes. Acta Phys Chem Szeged 21 11-18... 

Phosphorescence spectra of DTT and DTP were measured in MeOH/EtOH glass at 77 K. DTT and DTP exhibited phosphorescence with clear vibrational structure. This finding is attributed to the rigid structure caused by the bridging group at the 3,3 positions of 2,2-bisthiophene 84. The triplet energy of DTT and DTP estimated from the 0-0 bands of the phosphorescence spectra are given in Table 9. 

In 1962, Parker and Hatchard described a photoelectric spectrometer for phosphorescence measurements with which they were capable of obtaining phosphorescence spectra, and of determining lifetimes and quantum efficiencies of a large number of organic compounds. This work stimulated intensely the interest in the phosphorimetry of diverse chemical analytes [5], and one year later, Wine-... 

Describe the essential features in the measurement of fluorescence and phosphorescence spectra, including any precautions necessary. 

Fig. 3.1. Perrin-Jablonski diagram and illustration of the relative positions of absorption, fluorescence and phosphorescence spectra.

The aromatic amino acids each have two major absorption bands in the wavelength region between 200 and 300 nm (see reviews by Beaven and Holiday(13) and Wetlaufer(14). The lower energy band occurs near 280 nm for tryptophan, 277 nm for tyrosine, and 258 nm for phenylalanine, and the extinction coefficients at these wavelengths are in the ratio 27 7 l.(14) As a result of the spectral distributions and relative extinction coefficients of the aromatic amino acids, tryptophan generally dominates the absorption, fluorescence, and phosphorescence spectra of proteins that also contain either of the other two aromatic amino acids. 

Phosphonofluoridate, methyl-, isopropyl ester, reaction with cyclohexaamylose, 23 237 Phosphoramidon, as inhibitor, 28 330,331 Phosphorescence spectra, transition-metal oxides, 31 121... 

Table 8. Triplet levels (cm l) of aromatic molecules obtained from oxygen perturbation and phosphorescence spectra, respectively (From Ref.

Fig. 27. Semilogarithmic plot of the nonradiative triplet rate constant against (E— o)/> for the normal and deuterated hydrocarbons listed in Ref. t)). The broken line, derived from phosphorescence spectra, is taken from Ref. t). The slopes of the two solid lines differ by a factor 1.35. (O.Ci-jjH, E = 4000 cm l 0 Ci fl Z>u, =5500 cm t). The following totally deuterated hydrocarbons are included benzene, triphenylene, acenaphtene, naphthalene, phenanthrene, chrysene, biphenyl, p-terphenyl, pyrene, 1,2-benzanthracene, anthracene (in the order of increasing /S). (From Siebrand and Williams, Ref. l)...

Fig. 28. Time-resolved phosphorescence spectra of quinoxaline in durene host observed at 1.38 K and at (a) 30 msec, (b) 450 msec, and (c) 1500 msec after excitation cutoff. The ordinate scale is normalized with respect to the 0 - 0" band. The numbers shown in (c) represent the vibrational frequencies (in wavenumber unit) measured from the 0 - 0" band (21639 cm r). The arrows indicate the bands whose relative intensities are remarkably enhanced at later times after the excitation cutoff. (From Yamauchi and Azumi, Ref. >)...

Yamauchi, S., Azumi, T. Observation of the phosphorescence spectra from the spin sublevels of low emissivity Quinoxaline. Chem. Phys. Letters 21, 603 (1973). 

The combination of Raman and phosphorescence spectra studied by Pawlopoulos with phenanzine gives information about a rather strong spin-orbit coupling in this molecule. 

The vibrational structure and polarization properties of the phosphorescence spectra of testosterone and two other 4-en-3-ones indicate that excitation to the lowest triplet state causes little change in geometry/ contrary to earlier... 

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