Band origin

In addition to the dependence of the intennolecular potential energy surface on monomer vibrational level, the red-shifting of the monomer absorption as a fiinction of the number of rare gas atoms in the cluster has been studied. The band origin for the Vppp = 1 -t— 0 vibration in a series of clusters Ar -HF, with 0 < n < 5, was measured and compared to the HF vibrational frequency in an Ar matrix (n = oo). The monomer vibrational frequency Vp p red shifts monotonically, but highly nonlinearly, towards the matrix value as sequential Ar atoms are added. Indeed, roughly 50% of the shift is already accounted for by n = 3. 

Units are cm throughout. Measurements are of band heads, formed by the rotational stmcture, not band origins. Figures in parentheses are differences variations in differences (e.g. between the first two columns) are a result of uncertainties in experimental measurements. 

In retrospect, by inspecting the literature, we find a confirmation of this variance (see for instance Ref. [67]). Peak intensities of bands originally assigned to Franck-Condon components of the excilonic emission have random relative intensities. This would not be possible if the bands were intrinsically vibronic. Since we know that the excilonic emission, as it is observed in single crystals, is rather sharp at low temperatures, we were forced to reconsider the assignment of the fluorescence of thin films. From the temperature dependence of the fluorescence effi-... 

It seems feasible that the 325 nm band originates from S5 the UV spectrum of which is still unknown. 

Nevertheless, the band-shift rule can be used to identify the geometries of each of the He2 Br2(X, v" = 0) conformers. Since the T-shaped He Bt2 feature associated with transitions of the (l,0)He Bt2 conformer is observed at - -4cm from the monomer band origin,... 

He Br2 complex, and transitions of it are observed at approximately +4 cm from the linear band or at approximately +14 cm from the monomer band origin. 

The action spectrum plotted in Fig. 7c was recorded in the Br2 B X, 14—0 region. Features associated with transitions of Hes Br2 complexes are expected to become prominent in this spectrum since the Av = —3 product is being probed. Again following the band-shift rule the features associated with transitions of the (3,0)He Br2 and (2,l)He Br2 conformers are observed at about +4 cm from the (2,0)He Bt2 and (l,l)He Br2 features. Since the (0,l)He- Br2 feature is shifted by about +10cm from the monomer band origin, and the (l,l)He Br2 feature is found at about +14cm, the weak feature observed at about +24 cm is tentatively attributed to transitions of the... 

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].

Raman optical activity is an excellent technique for studying polypeptide and protein structure in aqueous solution since, as mentioned above, their ROA spectra are often dominated by bands originating in the peptide backbone that directly reflect the solution conformation. Furthermore, the special sensitivity of ROA to dynamic aspects of structure makes it a new source of information on order-disorder transitions. 

In the early stage of the development of molecular conductors based on metal complexes, partially oxidized tetracyanoplatinate salts (for example, KCP K2 [Pt(CN)4]Br0.30-3H2O) and related materials were intensively studied [6], In this system, the square-planar platinum complexes are stacked to form a linear Pt-atom chain. The conduction band originates from the overlap of 5dz2 orbitals of the central platinum atom and exhibits the one-dimensional character. 

The electronic spectra of these materials recorded in chloroform solution appear to be dominated by intense bands originating from internal ligand transitions, metal-ligand and ligand-metal charge-transfer bands, whose intensities change markedly with changes in the population of the two spin states [7]. 

By contrast, in the CD spectrum of the p derivative (39), no bands were observed even at —80°C, as shown in Figure 4.19b. This is because the Cotton band of the p derivative is canceled by an oppositely signed CD band originating in an equivalent proportion of opposite screw sense helical segments (which may be referred to as masked helicity or masked circular dichro-ism ). The difference between the helical conformations of m and p derivatives may be due to the degree of steric hindrance of (S>2-methylbutoxyphenyl rings, since the p derivative may have enough space to freely rotate the... 

As pointed out earlier, RR spectroscopy is a powerful tool for an unambiguous distinction between coordinated and uncoordinated phenoxyl radicals. Upon excitation in resonance with the n —> ir transition of the phenoxyl, the RR bands originating from the modes ula (-1500 cm-1 C-O stretching) and uSa (-1600 cm-1 C=C stretching) are enhanced and clearly detectable. The exact positions of these bands as well as their RR intensity ratio can be used to distinguish between coor-... 

Efficient Calculation of Highly Excited Vibrational Energy Levels of Floppy Molecules The Band Origins of Hj up to 35000 cm-1. 

Figure 8.4 The v = 6 C-H overtone spectrum as determined by photoacoustic absorption (Hall, 1984) for increasing size alkynes. Each panel contains the molecular formula and the density of vibrational states per cm 1. The band origin does shift some with size but is roughly at 18450 cm"1 for all the molecules shown (see also Kerstel et al., 1991).

There are two absorption bands of S02 within the range 3000-4000 A. The first is a weak absorption band and corresponds to the transition to the first excited state (a triplet). This band originates at 3880 A and has a maximum around 3840 A. The second is a strong absorption band and corresponds to the excitation to the second excited state (a triplet). This band originates at 3376 A and has a maximum around 2940 A. 

For instance, LIF experiments, carried out on the heterochiral complex between F and M = (7 )-2-butanol, indicate the presence of three new bands at —136, — 114, and — 73 cm from the band origin of the bare F. Similar experiments on the homochiral complex between F and M = (5)-2-butanol exhibit two new bands at — 125 and — 69 cm from the band origin of the bare F. HB experiments show that four different isomers coexist in the jet, two of them corresponding to the... 

The mass resolved lcR2PI spectrum of the bare chiral chromophore Cr = (R)-(+)-l-phenyl-1-propanol, shows three intense signals at 37577 (A), 37618 (B), and 37624 cm (C) in the electronic Sj — Sq band origin region. A similar triplet falls at 38106, 38148, and 38155 cm . This pattern is common to substituted arenes and is interpreted as due to three stable conformers. Quantum chemical calculations at the RF1F/3-21G and B3LYP/6-31G levels of theory confirm this hypothesis. 

Band shifts of the a peaks, relative to the band origin A of bare C. ... 

Fig. 9 Diagram of the band origin shifts Ai of the molecular complexes between ( )-(+)-l-pheny 1-1-propanol (C ) and primary and secondary alcohols and amines. The circles refer to primary alcohols (open circles = full circles = the diamonds refer to secondary alcohols and amines (open diamonds = Av, full diamonds = Av/ ).

Table 4. Band origin, pure vibrational matrix element and strength of vibration-rotational...

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