Absorption spectra, recording

Examine the seven absorption spectra, record the Amax values of absorption peaks comment upon the effect of —OH and —NH2 groups upon the absorption spectrum of benzoic acid, and of hydrochloric acid and sodium hydroxide upon the spectra of the two substituted benzoic acids. 

FIGURE 8.7 Transient absorption spectra recorded 3ps following excitation for zeaxanthin (a) and ACOA (b). The spectra were measured with excitation at 400 nm (H-aggregates), 485 nm (monomers), and 525 nm (J-aggregates). 

Figure 2. Diffuse reflectance UV-visible absorption spectra recorded as a function of time after the mixing of solid DPB and H0 57ZSM-5 (a) and after of solid DPB and H6 6ZSM-5 (b)...

Fig. 4.5 Structures and visible absorption spectra recorded in DMSO of BF1-BF3 and BF4-BF6...

Figure 4.7 Electronic-absorption spectra recorded in toluene of a mixture of (ethoxycarbonyl)-methylene-bridged fullerenes 114 with the relative ratio (1 1 3) (—), of pure isomer 114a (- ), and of Qq (—) [129. ...

Figure 13 Transient absorption spectra recorded before hvs i (O) and immediately after ( ) and 200 nsec (A) and 1 ps (A) after hvs32 during PR-LFP of c-St (5x10 M) in DCE (a). Kinetic traces illustrating time profiles of AO.D.480 (b) and AO.D.515 (c) as a function of time after e. ...

Figure 14 Transient absorption spectra recorded immediately after e (O), and before ( ) and immediately after (A) hvs22 during PR-LFP of a mixture of -St (5 x 10 M) and Bp (1 x 10 M) in DMF. The delay time of hv i from e was 75 nsec.

Analysis of the transient absorption spectra recorded at 100 ns allows for the determination of the prompt relative yields of the G /G(-H) radicals, I g (<100 ns). This yield is probably due, in part, to the oxidation of the guanines by the 2AP + radical cations [11]. Assuming that the 2AP radical cations decay only via the deprotonation of 2AP (rate constant ku) and hole transfer from 2AP + to guanine (fct), the prompt yield Og may be expressed as follows ... 

Fig. 1. Transient absorption spectra recorded in ethylene glycol after photoionisation of the solvent by a 263 nm laser pulse.

Fig. 4. Cw absorption spectra recorded before and after the one pulse experiment (left hand side) respectively the two pulses experiment (right hand side).

Fig. 1-left gives a general overview of the differential absorption spectra recorded for the free chromophore, oxyblepharismin, dissolved in DMSO for reference the steady-state absorption and (uncorrected) fluorescence spectra are also given below, in dotted lines. At all pump-probe delay times, the overall picture is a superposition of the structured bleaching and gain bands, as expected from the steady-state spectra, and broad transient absorption bands around 530 nm and 750 nm (weaker). These apparently homothetic spectra are very similar to... 

The W(CO)4(4-Me-phen) complex also displays a number of spectroscopic features that lend themselves to utility as a probe [106], Figure 20 depicts electronic absorption spectra recorded from a 0.25-mm thickness film of a photosensitive acrylate system comprising a 1 1 (by weight) ratio of TMPTA and medium weight PMMA. Incorporated are the photoinitiators benzophenone (4% by weight) and 4,4/-bis(dimethylamino)benzophenone (0.5% by weight), and the probe complex W(CO)4(4-Me-phen) (0.3% by weight). The major absorption feature in this acrylate film is observed at 353 nm and is due to the photoini-... 

Figure 5.6 (a) UV-vis absorption spectra recorded during the successive deposition of 10 bilayers of... 

The charge carriers formed upon absorption of light (reaction (7.1)) can recombine in a radiative or non-radiative way according to reactions (7.12) to (7.15). This is clearly seen from the rather rapid depletion of the transient absorption spectra recorded during laser flash photolysis studies (see Fig. 7.4). 

UV spectroscopy and a polyvinyl chloride (PVC) film as matrix at 10-15 K were extensively used to detect, or to infer from the absorption spectra recorded, the intermediacy of thiazirenes 2 on thermolysis or photolysis <1978J(P1)746>. 

Fig. 16. Comparison between the absorption spectra recorded in liquid ethane-1,2-diol at early time after two-photon ionisation (Fig. 13) at 295 K and the absorption spectra of the solvated electron obtained at high temperature by pulse radiolysis.

A fine example of the use of pulse radiolysis technique in combination with steady-state product distribution is the recent study by Schuler and co-workers to probe charge distribution in aromatics. Their initial studies on biphenyf which were extended recently to phenof have been concerned with the determination of relative yields at o-, m- and -positions to examine the substituent effects on charge distribution. For example, Fig. 2 shows the contour plot of HPLC chromatographic data obtained in the OH radical reaction following the irradiation of phenol in the presence of the oxidant ferricyanide. Figure 3 shows the transient absorption spectra recorded in the reactions of OH and Ng radicals with phenol. The absorption... 

Fig. 6. Transient absorption spectra recorded 2 ps after the pulse obtained in the reaction of "OH with (A) 1,2-dichlorobenzene (x), 1,3- dichlorobenzene without (A) and with 0.2 M tert-butyl alcohol (o), (B) 2-bromotoluene ( ), 3-bromotoluene (o) and 4-bromotoluene ( ). Dose per pulse = 2 krad pH = 7 [solute] = 10 mol dm . [Reprinted with permission ftom Ref. 15. Copyright 1994, American Chemical Society.]...

The reaction mechanism was also confirmed by a series of absorption spectra recorded on a rapid-scan spectrophotometer. 

Fig. 12. In situ absorption spectra of Ru-red in an aqueous solution (pH 7.4 phosphate buffer) measured during a voltammetric scan at 5 mVs using a thin layer ITO cell. The direction of the absorbance change and the potential range are indicated in the figure. (A) Absorption spectra recorded during the oxidative scan from — 0.1 to 0.32 V/Ag wire. Inset cyclic voltammogram recorded during the in situ absorption spectral measurements at 5 mVs". (B) Absorption spectra recorded during the oxidative scan from 0.32 to 1.0 V/Ag wire and during the reductive scan from 1.0 to — 0.1 V/Ag wire. Spectrum a Absorption spectrum recorded in the beginning of the scan. (Reproduc with permission from The Royal Society of Chemistry)...

Figure 13. Transient absorption spectra recorded on the microsecond time scale upon 532-nm CT excitation of (A) quinolinium tetracarbonylco-baltate and (B) Af-methyl-4-cyanopyr-idinium tetracarbonylcobaltate in acetone showing Co(CO)4 radical (at 790 nm) and quinolinyl (at 540 nm) or cyanopyridinyl (at 370 nm) radicals, respectively [118].

Figure 16. The electrochemically induced dethreading/rethreading processes associated with pseudorotaxane [6 4] + and the absorption spectra recorded (MeCN, 298 K) before (center) and after oxidation (top) or reduction (bottom) [6].

Figure 24. (a) Transient absorption spectra recorded after excitation of 19 in DMF with a 30-ps laser pulse at 598 nm delay times are given on the traces, (b) Typical kinetic trace observed for the conditions as in (a), (c) Transient absorption spectra recorded after excitation of 19 in DMF with a 30-ps laser pulse at 532 nm. (d) Typical kinetic trace observed for the conditions as in (c). 

Figure 2. a) Transient absorption spectra recorded after excitation of di- -butyltetramethylindo-carbocyanine benzyltriphenylborate in benzene solution with a 18 ps laser pulse. Negative absorbance related to the bleaching of the dye absorption. The band at Amax = 430 nm is attributed to the presence of the cyanine dye radical b) transient absorption spectra recorded after excitation of naphthyltriphenyl borate in benzene solution with a 18 ps laser pulse. The new feature is attributed to the presence of the (2-naphthyl)methyl radical c) the difference spectrum obtained by subtracting spectrum A from spectrum B the maximum at 385 nm is characteristic for the 2-methylnaphthyl radical. Data are taken from [25],... 

---