IR-UV double resonance

IR-UV double resonance also selective for S and C Reaction of both Isotopes with high selectivity (high fluence)... 

Fehrensen B, Hippier M and Quack M 1998 Isotopomer selective overtone spectroscopy by ionization detected IR + UV double resonance jet-cooled aniline Chem. Phys. Lett. 298 320-8... 

K. Le Barbu Debus, N. Seurre, F. Lahmani, and A. Zehnacker Rentien, Formation of hydrogen bonded bridges in jet cooled complexes of a chiral chromophore as studied by IR/UV double resonance spectroscopy. 2 Naphthyl 1 ethanol/(methanol)n j 2 complexes. Phys. Chem. Chem. Phys. 4, 4866 4876 (2002). 

As pointed out before, the IR/UV double resonance spectra of the complexes between F and the enantiomers of 2-amino-1-propanol (alaninol) exhibit spectral features due to structures involving not only the expected intermolecular hydrogen bonding (either OH- - -O or OH- - -N), but also extensive intramolecular OH- - -N and OH- - -TThydrogen bonding. Similar intramolecular interactions are present in the isomeric [C/j-M/ r], [C/j-M/ s], and [C/j-Mss] adducts as well. 

Plutzer C, Nir E, de Vries MS, Kleinermanns K (2001) IR-UV double-resonance spectroscopy of the nucleobase adenine. Physical Chemistry Chemical Physics 3 5466-5469. 

Keywords DNA Bases, Base Pair, Laser Desorption, REMPI, IR-UV Double Resonance... 

State of the art for spectroscopic analysis in the gas phase is currently IR-UV double resonant spectroscopy [8-12], schematically depicted in Figure 12-1. This... 

Figure 12-1. Schematic diagram to illustrate double resonance techniques, (a) REMPI 2 photon ionization. The REMPI wavelength is scanned, while a specific ion mass is monitored to obtain a mass dependent SI <- SO excitation spectrum, (b) UV-UV double resonance. One UV laser is scanned and serves as a burn laser, while a second REMPI pulse is fired with a delay of about 100 ns and serves as a probe . The probe wavelength is fixed at the resonance of specific isomer. When the burn laser is tuned to a resonance of the same isomer it depletes the ground state which is recorded as a decrease (or ion dip) in the ion signal from the probe laser, (c) IR-UV double resonance spectroscopy, in which the burn laser is an IR laser. The ion-dip spectrum reflects the ground state IR transitions of the specific isomer that is probed by the REMPI laser, (d) Double resonance spectroscopy can also use laser induced fluorescence as the probe, however that arrangement lacks the mass selection afforded by the REMPI probe...

To access the ground state the IR-UV double resonant technique has proven to be very powerful. This approach provides ground state vibrations in the 500-4000 cm-1 range with isomer selection. This has made it possible to obtain tautomer selective and cluster structure selective spectroscopy. This ability to obtain... 

Figure 12-2. IR-UV double resonant and R2PI spectra of three guanine-cytosine cluster structures. Stick spectra show calculated frequencies for modes, indicated in line types according to the key in the top panel. The relevant numbering is indicated in the structure (c). Structure (a) is corresponds to the Watson-Crick structure and is not observed for the unmethylated bases...

Figure 12-3. IR-UV double resonance spectrum of GC (structure C) in the mid-IR frequency range (recorded at the FELIX free electron laser facility), compared with three types of ab intio calculations. Harmonic frequencies were obtained at the RI-MP2/cc-pVDZ, RI-MP2/TZVPP, and semiempirical PM3 levels of electronic structure theory. Anharmonic frequencies were obtained by the CC-VSCF method with improved PM3 potential surfaces [30]...

Figure 12-4. IR-UV double resonance spectrum of guanosine-cyclic-phosphate...

Figure 12-5 summarizes the observed structures of various DNA base pairs in the gas phase, as determined by IR-UV double resonance spectroscopy. Open circles indicate the sites at which the ribose group is attached in the nucleosides. The structures in columns (b) and (c) are the ones observed experimentally. The structures in column (a) were not observed. For G-C pairs the structure in column (a) is the Watson-Crick structure. Abo-Riziq et al. observed this structure when the bases were derivatized in the ribose position (N9 for guanine and N1 for cytosine), however, in that case the UV spectrum was very broad [42], One of the most remarkable features of these data is thus that some of the biologically most important structures so far remain unobserved in the gas phase. The structures of column (a)... 

Figure 12-6. IR-UV double resonance spectra of guanine dimers with 0, 1, and 2 water molecules...

Figure 12-8. REMPI spectra of various cytosine dimers. Asterisks indicate origins of different structures as determined by UV-UV double resonance spectroscopy. The corresponding structures, as determined by IR-UV double resonance spectroscopy are shown below...

UV-UV double resonance spectroscopy to determine origins of separate isomers, followed by IR-UV double resonance to determine their structures. The resulting structures appear in the figure. 

Figure 12-2 shows data we obtained for three isolated GC base pair structures. Row A shows results for the Watson-Crick (WC) structure, while rows B and C represent the second and third lowest energy structures, respectively, which are not WC. The second column shows the IR-UV double resonance data, compared with the ab initio calculations of the vibrational frequencies. These data allow us to assign the structures. The third column shows the UV excitation spectra, measured by resonant two-photon ionization (R2PI). The UV spectrum is broad for the WC structure (A) and exhibits sharp vibronic lines for the other structures. 

The jet-cooled species can be studied using standard laser techniques (Figure 13-4a) like laser-induced fluorescence (LIF or fluorescence excitation spectroscopy) or R2PI, as well as using their sophisticated double-resonance variants, like UV/UV or IR/UV double resonance spectroscopy (Figure 13-4b and 4c), to investigate molecules or clusters existing under various isomeric forms... 

H. J. Neusser and K. Siglow, High-resolution ultraviolet spectroscopy of neutral and ionic clusters hydrogen bonding and the external heavy atom effect, Chem. Rev. 100,3921-3942 (2000). Y. Matsumoto, T. Ebata, and N. Mikami, Structures and vibrations of 2-naphthol-(NH3) (n = 1-3) hydrogen-bonded clusters investigated by IR-UV double-resonance spectroscopy, J. Mol. Struct. 552, 257-271 (2000). 

T. Watanabe, T. Ebata, S. Tanabe, and N. Mikami, Size-selected vibrational spectra of phenol-(H20) (n = 1-4) clusters observed by IR-UV double resonance and stimulated Raman-UV double resonance spectroscopies, J. Chem. Phys. 105, 408-419 (1996). 

P. Bering, Structure and vibrations of the phenol-ammonia cluster, J. Chem. Phys. 102, 9197-9204 (1995). (c) S. Tanabe, T. Ebata, M. Fujii, and N. Mikami, OH stretching vibrations of phenol-(H20) (n = 1-3) complexes observed by IR-UV double-resonance spectroscopy, Chem. Phys. Lett. 215, 347-352 (1993). (d) D. Michalska, W. Zierkiewicz, D. C. Bien ko, W. Wojciechowski, and T. Zeegers-Huyskens, Troublesome vibrations of aromatic molecules in second-order Moller-Plesset and density functional theory calculations infrared spectra of phenol and phenol-OD revisited, J. Phys. Chem. A 105, 8734-8739 (2001). 

Fig. 4.9 IR spectra of aniline in a supersonic beam from Ref. [41], The upper trace was obtained by IR-UV double-resonance spectroscopy with the use of the nanosecond laser system. The inset shows the expanded spectrum in the CH stretch region. The lower trace is the ionization gain IR spectrum obtained with the picosecond laser system (Reprinted with permission from Ref. [41]. Copyright (2005), American Institute of Physics)...

Fig. 8.18 Term diagram of IR-UV double resonance for measurements of collision-induced intramolecular vibrational transitions in the D2CO molecule [1041]...

F. 1 Schematic representation of the molecular beam set-up equipped with a laser desorption source and a reflectron Time-of-Flight mass spectrometer used for IR-UV double resonance experiments at the FELIX Facility. The inset shows details of a typical laser desorption source... 

The conformer selectivity in IR-UV double resonance methods relies on the excitation bands of different conformers being resolvable in the UV spectrum. For tmresolved UV spectra, indicating either short excited state lifetimes (<1 ns) or strong conformational heterogeneity, the IR-UV ion dip scheme can be modified by introducing either a femtosecond ionization laser (IR femtosecond multiphoton ionization) [80,81] or an additional IR step (IR-IR-UV spectroscopy) [21,82-84]. 

Tanabe S, Ebata T, Fuji M, Mikami N (1993) OH stretching vibrations of phenol-(H20)n(n = 1-3) complexes observed by IR-UV double-resonance spectroscopy. Chem Phys Lett 215(4) 347-352... 

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