X fluorescence

Fluorometry and Phosphorimetry. Modem spectrofluorometers can record both fluorescence and excitation spectra. Excitation is furnished by a broad-band xenon arc lamp foUowed by a grating monochromator. The selected excitation frequency, is focused on the sample the emission is coUected at usuaUy 90° from the probe beam and passed through a second monochromator to a photomultiplier detector. Scan control of both monochromators yields either the fluorescence spectmm, ie, emission intensity as a function of wavelength X for a fixed X, or the excitation spectmm, ie, emission intensity at a fixed X as a function of X. Fluorescence and phosphorescence can be distinguished from the temporal decay of the emission. 

Figure 13. Action spectrum of the linear He I Cl complex near the He + I Cl(By = 2) dissociation limit obtained by scanning the excitation laser through the ICl B—X, 2-0 region and monitoring the l Cl E—>X fluorescence induced by the temporally delayed probe laser, which was fixed on the l Cl E—B, 11-2 band head, (a). The transition energy is plotted relative to the I Cl B—X, 2-0 band origin, 17,664.08 cm . Panels (b), (c), and (d) are the rotational product state spectra obtained when fixing the excitation laser on the lines denoted with the corresponding panel letter. The probe laser was scanned through the ICl B—X, 11-2 region. Modified with permission from Ref. [51].

Five anticonvulsants including valproic acid were determined by the Abbott TD x fluorescence polarization immunoassay automatic analyzer. Recoveries were 94.8-106% and the coefficients of variations were 1.0-9.7% [23], Fluorescence polarization immunoassay and enzyme immunoassay were compared for the determination of free valproic acid in serum [24], Good correlation (R = 0.9992) was obtained between the two assays. Higgins [25] reported on the determination of valproic acid in serum by enzyme immunoassay with use of EMIT reagents and the Abbot ABA-200 analyzer. Responses were rectilinear up to 150 mg/L. 

Samples of Y faujasites were prepared by sodium exchange of a starting ultrastable Y zeolite (H form, denoted in the following as USY). Global Si/Al ratio is 16 according to X fluorescence measurements framework Si/Al is 21 as measured by 29Si MAS NMR. 

Yu H, Xi B, Ma W, Li D, He X. Fluorescence spectroscopic properties of dissolved fulvic acids from salined flavo-aquic soils around Wuliangsuhai in Hetao Irrigation District, China. Soil Sci. Soc. Am. J. 2011 75 1385-1393. 

Huang, X., Fluorescence polarization competition assay the range of resolvable inhibitor potency is limited by the affinity of the fluorescent ligand, /. Biomol. Screen., 8, 34,2003. 

Table 1 Linear spectral parameters of 3, 5, 6 and 11 absorption, and fluorescence, X fluorescence quantum yields, fl, and orientation polarizabilty of the solvents. A/... 

DNA]x = concentration of the unknown solution of DNA in /xg/mL [DNA]std = concentration of the standard solution of DNA in /xg/mL DNA-std = fluorescence yield of the standard DNA solution ADNA-x = fluorescence yield of the standard DNA solution after incubation with ribonuclease... 

The transition to the C B- state of H 0 was achieved by a two photon absorption of KrF laser light near 248 nm (32). The OH(A-X) fluorescence excitation spectrum in the 247.9-248.5 nm range follows the rotational structure of the C B -+ X A transition. However, (i) the OH(A-X) fluorescence spectrum produced by the two photon dissociation of H 0 has a maximum population at N = 14, while single photon absorption near 124 nm generates OH fluorescence spectrum with a maximum population at N = 20 (ii) only absorption to Ka= 1 (and not Ka= 0 where K is the rotational angular momentum about the a axis) of the ClB-L state predissociates into 0H(a2%) + H probably through the B A state. Apparently, the two-photon absorption near 248 nm predominantly populates the c b state, while the single photon process populates the B A near 124 nm. 

The NO rotational excitation is very large and direct dissociation was suggested. Ebata et al. (109) have found the A+X fluorescence of CH3O (process 44) at the 193 nm photolysis. The CH3O A state is highly rotational and vibrationally excited. 

Therefore, the primary excitation causes the emission of X fluorescence or Y fluorescence depending on the kind of excitation. Under constant irradiation of the scintillator the fluorescence intensity L is proportional to the complete technical quantum efficiency Q ... 

FLC-350 X Constant flow-rate pump X X Fluorescence Pos. to connect... 

Figure 4-2. Potential energy diagram of the Hg(3P,) + Cl2 reaction. The entrance channel (on the left) and the exit channel (HgClB2X + -> X + fluorescence) are indicated.

From the onset of the B-X fluorescence in Figures A and 6a and the known Franck-Condon factors for the B-X transition, it can be determined that the highest "hot band" vibrational quantum level populated in the ground electronic, state of Na2 is v" = 18. 

Figure 7. Continuation of spectra presented in Fig. 6. Key a, excitation spectrum (Ar ion pumped coumarin 7) showing Na B n — AT 2/ fluorescence b, Ps/i Na laser induced atomic fluorescence c, Pi/i laser induced atomic fluorescence and d, Fast photoluminescence scans indicating relative magnitudes of Na D-line and Noi B-X fluorescence (tick marks indicate v = 17,000 and 21,000 cm and indicates laser excitation frequency.

Perkins, W. A., Leighton, P. A., Grinnell, S. W., Webster, F. X., Fluorescent Atmospheric Technique for Mesometeorological Research, Proceedings of 2nd National Air Pollution Symposium, Stanford Research Institute, Pasadena, Calif., 1952. 

Li Y, Ma Q, Wang X, Su X. Fluorescence resonance energy transfer between two quantum dots with immunocomplexes of antigen and antibody as a bridge. Luminescence 2007 22 60-6. 

Peptide sequence ccxcc x= Fluorescence quantum yield of complex Apparent k[Pg.434]

Case I [(A ,+A o)/ +this case we find that the preexponential constant in (6) is positive and that the A(l) fluorescence signal rises with the rate of the X decay, namely [(A ,+ A o)P +A xj X2l-Consequently, a plot of either the decay rate of X fluorescence or the rise rate of A(l) fluorescence vs. pressure of A gives a line whose slope is (A, + Aq). The decay of the A(l) signal takes place at the rate kyP, so that a plot of this rate vs. gives a line whose slope is Ay. Finally k can be obtained, for example, from a plot of the X fluorescence decay rate vs. 

Case II AvFa>[(A,+ Aq)/ + AxjFxJ. For this case we find that the preexponential constant in (6) is negative and that the identities of the rise and decay rates for the A(l) fluorescence are reversed. The decay of the A(l) fluorescence is now equal to the decay of the X fluorescence, while the rise of the A(l) fluorescence is equal to kyPj. The constant Ax may still be obtained from the decay of X fluorescence as a function of Pxj-... 

For either of the above cases the sum (Ai + Aq) may be obtained from each of two sources. This redundancy offers a valuable check as to whether the assumptions of the kinetic scheme are vahd. However, it is not true that the time dependence of either the A(l) or X fluorescence gives a separate value for Aq or A,. This information must be obtained from the ratio of the two signal amplitudes. 

The value of A, is obtained by taking the ratio of the amphtude of the A(l) fluorescence to the amplitude of the X fluorescence. As seen from... 

Generalization of the kinetic scheme to cases where E- V transfer from X to A populates vibrational levels higher than o = 2 becomes increasingly complicated. Under certain conditions, however, the interpretation of the fluorescence signals remains relatively simple, and the amplitude ratio of A(l) to X fluorescence still yields the numerator of Q.E. = 2 A ,/2y( ,. The conditions under which these simple relations hold are outlined elsewhere. ... 

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