Isamu Suzuka

Single vibronic level fluorescence from n, π* state of pyrazine vapor

Abstract Fluorescence spectra from various single vibronic levels of the 1 B 3u state of pyrazine- h 4 and — d 4 vapors have been observed and analyzed, leading to unambigous assignments of a number of absorption bands. Nine excited state fundamentals have been established for pyrazine- h 4 . Ground state fundamentals of b 2g and a u species have been confirmed as well. From the observations of anharmonic couplings between the vibrations belonging to different symmetry in D 2h point group, lowering of molecular symmetry in 1 B 3u state has been suggested.

Raman spectra of pyrazine resonant to the S2(π,π*) state and the geometry in excited state

Abstract Raman spectra resonant to the S 2 (π,π * ) state of pyrazine vapor consist of fundamentals, overtones and combinations of only two totally symmetric vibrations, ν 1 and ν 6a . Combining the Raman with the absorption spectra it is experimentally verified that the molecules deformation upon excitation is reflected on the resonance Raman spectra.

Electronic spectra of jet-cooled 1-phenylpyrrole: Large-amplitude torsional motion and twisted intramolecular charge-transfer phenomenon

The fluorescence excitation spectrum and the single vibronic level dispersed fluorescence spectra in the region of the S0⇆S1 transition were measured for jet-cooled 1-phenylpyrrole. The 0–0 band was observed at 35 493 cm−1. Long and low-frequency progressions with somewhat irregular intensity distributions appeared on both spectra, and were assigned to torsional motion. The torsional energy levels in the S0 and S1 states were obtained up to 25 and 16 quanta, respectively. The torsional potentials in both states could be determined from the sufficient number of energy levels observed. In the S0 state the most stable conformation was determined to be a twisted form with a dihedral angle of 38.7°, where the planar barrier height was calculated to be 457 cm−1, and the perpendicular to be 748 cm−1. On the other hand, it was discovered that 1-phenylpyrrole in the S1 state also had a twisted form with a somewhat smaller dihedral angle of 19.8°, and that the barrier to planarity was 105 cm−1 and to perpendiculari...

Single vibronic level flourescence from pyrazine vapour by dye laser excitation

Flourescence spectra have been obtained by tuning the laser light to various single vibronic levels of the 1B3u(n, π*) state of pyrazine vapour. Spectra are interpreted in terms of ground state frequencies and conclusive evidence for the assignment of the 6a, 9a, 10a and 16b modes in the n, Π* excited state are given.

Single vibronic level fluorescence spectra of pyrazine and their relation to vibronic coupling

Abstract Single vibronic level fluorescence spectra of pyrazine- h 4 and - d 4 are reported and the intensity distributions of the lone b tg mode in these spectra are analyzed in terms of a vibronic coupling model.

Assignments of lowest triplet state in Ir complexes by observation of phosphorescence excitation spectra at 6 K

We tried the assignment of the origin of phosphorescent bands in Ir complexes. It is important to elucidate the luminescent mechanism in order to design organic light-emitting devices (OLEDs) besed on new materials. The Stokes shift between the phosphorescence and phosphorescence excitation spectra of Ir complexes such as fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)3], fac-tris(2-(2-thienyl)pyridine) iridium(III) [Ir(thpy)3], bis(2-phenylpyridine) iridium(III)benzo[h]quinoline [Ir(ppy)2bzq], fac-tris(benzo[h]quinoline) iridium(III) [Ir(bzq)3] and bis[(4,6-difluorophenyl)pyridinato](picolinato) iridium(III) [FIrpic] was measured in a solution and (phenyl)4Sn at 6 K. The amount of Stokes shift corresponds to the nature of the lowest triplet state. We discovered that the amount of Stokes shift clearly differs depending on whether the lowest triplet state of each Ir complex is triplet metal-to-ligand charge transfer (3MLCT) or 3π–π*. Namely, the case of 3MLCT shows a large shift, while the case of 3π–π* shows a small shift. We also present the resolved phosphorescence and phosphorescence excitation spectra of Ir complexes in (phenyl)4Sn. The sharp bands were assigned to the 3π–π* transition, and the broad bands were assigned to the 3MLCT state. The nature of the lowest triplet state is also discussed on the basis of resolved spectra.

Physical and chemical interface effects on Mie plasmon absorption of sodium nanoclusters passivated with CH4−nCln (n=1–4) molecules

Abstract We have examined the metal/medium interface effects on the optical absorption due to Mie plasmon resonance of sodium nanoclusters passivated with CH 4− n Cl n ( n =1–4) molecules. The redshifted bands are observed around 600 nm in each Na/CH 4− n Cl n aerosol generated by the gas-aggregation technique with a reactant nozzle (GATRN). The peak energies are also redshifted with increasing the reactant-gas flow rates. The dielectric coated metal-particle model predicts that the sodium nanoclusters passivated with CH 4− n Cl n form in the aerosols and that the peak redshifts are due to the dielectric-shell growth and static charge transfer at metal/medium interface.

S1-State Internal Conversion of Isolated Azulene Derivatives

The S0-S1 hole-burning spectra of azulene and its derivatives, 1-methyl, 2-methyl, 4-methyl, 1-cyano, and 2-cyanoazulenes, were measured under the isolated condition in order to gain an insight into the internal-conversion mechanism. The width of every 0-0 band was dependent on its transition energy and independent of the density of the S0-state vibrational levels isoenergetic to its zero level of the S1 state. On the contrary, the vibronic-band broadening of each molecule progressed in proportion to the vibrational excess energy of the S1 state. In the low-energy region, widths gradually increased, which is attributed to the normal internal conversion. A drastic increase was observed in the medium-energy region in azulene and three methyl derivatives but not in the two cyano ones. This is considered to be the onset of the relaxation process due to the conical intersection suggested by Bearpark et al. [J. Am. Chem. Soc. 1996, 118, 169]. Anomalous width behavior was found for two vibronic bands whose widths were still narrow even above the onset. One was 0 + 2659 cm(-1) band of azulene, that had been already reported by Ruth et al. [Phys. Chem. Chem. Phys. 1999, 1, 5121], and we could reproduce it by the hole-burning method. Another was 0 + 2878 cm(-1) band of 2-methylazulene. This is the vibronic selectivity in competition between the relaxation process and the normal internal conversion. The amplitude vectors of these modes were similar, including the in-plane bending of the CH bond and the stretching of the transannular bond.

Design of a novel G-quenched molecular beacon: A simple and efficient strategy for DNA sequence analysis

G-quenched MBs are devised from readily available starting materials and used for sequence specific DNA detection with high efficiency.

Ion-induced sensitized phosphorescence excitation spectra of halobenzenes in supersonic jets

Abstract The sensitized phosphorescence and fluorescence excitation spectra of several halobenzenes in supersonic jets have been observed. It was found that the sensitized phosphorescence excitation spectra of some molecules exhibit an unusual feature in comparison with the corresponding fluorescence excitation spectra and that they are practically identical with the MPI spectra. The unusual feature arises from generation of the sensitized emission by collision of the ions produced by MPI with a phosphor. The mechanism of the ion collisional emission is discussed.