Ikuzo Tanaka

Infrared diode laser spectroscopy of the NO3 ν3 band

The N–O degenerate stretching band ν3 of the NO3 radical has been studied in the gas phase by infrared tunable diode laser spectroscopy. The NO3 radical was generated by the reaction of NO2 with an excess of O3. Zeeman modulation was employed to observe the paramagnetic absorption lines of 14NO3 and 15NO3 in the wavelength regions 1480–1500 and 1463–1479 cm−1, respectively. Only K’’=3n (n denoting an integer) transitions were observed, and the N’’=even members were missing from the K’’=0 manifold. These observations indicate that the NO3 radical belongs to D3h symmetry in the 2A2’ ground electronic state. The observed spectrum was analyzed using a symmetric‐top vibration‐rotation Hamiltonian including the spin‐rotation interaction. The main parameters thus obtained for 14NO3 are B3=0.455 22(11), C3=0.227 13(6), Cζ3=0.044 79(11), q3=0.001 624(33), t3= 0.000 000 458 0(43), B0=0.457 46(12), C0=B0/2 (fixed), ebb=0.0280(27), and ecc=0.1197(36) for v3=1, ebb=0.0277(28), and ecc=0.1117(34) for v=0, and ν0=1492.3...

Study of higher excited singlet states of zinc(II)‐tetraphenylporphin

The mechanism for the production of the S2 state fluorescence following the excitation to the S1 states of zinc (II)‐tetraphenylporphin has been investigated by using two‐photon absorption and optical–optical double resonance techniques. The main process populating the S2 state is found to be a stepwise two‐photon absorption through the S1 state (the Q state) even by the excitation of relatively low power density (<5×1015 photons cm−2 pulse−1) of a nitrogen pumped dye laser. The absorption cross sections σ1n of the Sn ← S1 transition are determined from the kinetic analyses based on the two‐photon absorption measurement. The Sn ← S1 absorption spectrum obtained is structureless and its σ1n values vary from 4.74×10−16 to 1.02×10−15 cm2 molecule−1 in the wavelength region of 490–560 nm. This observation suggests that the corresponding Sn ← S1 transition possesses a strongly allowed nature and there exists a higher excited singlet state of gerade symmetry in the 17 800–20 400 cm−1 region above the ground sta...

A reinvestigation of the NO3 1492 cm−1 band

Ishiwata et al. [J. Chem. Phys. 82, 2196 (1985)] have recently observed an infrared diode laser spectrum of NO3 in the 1492 cm−1 region and have assigned it to the ν3 band in the X2A’2 state. However, some of the derived constants such as the Coriolis coupling and spin–rotation constants did not conform well with expected values. In the present study, the observation was extended so as to take combination differences, which led us to revise the previous assignment slightly and to remove all the anomalies in the lower (i.e., ground) state. A most important result of the present study is that a spin–orbit interaction constant aeff‖〈Lz〉‖ =0.17 cm−1 is indispensable to explain the spin splitting observed for the upper state. The first‐order Coriolis coupling constant of the upper state (ζ=0.19) remains essentially the same as in the previous study and differs considerably from the value calculated for the ν3 state (ζ=0.7). Possible explanations of these data are discussed in some detail to obtain more inform...

Ã→X̃ fluorescence spectra of CH3O and C2H5O generated by the Arf laser photolysis of alkyl nitrites

Abstract The A → X system fluorescence spectra of CH3O and C2H5O have been obtained following the 193 nm photolysis of methyl and ethyl nitrites. These species are produced in highly rotationally and vibrationally excited states. The OO band is at 31530 cm−1 for CH3O and at 29200 cm−1 for C2H5O. The collision-free fluorescence lifetimes of the A state are independent of the levels of the CO stretching vibrational mode and are measured to be 2.2 μs for CH3O and 1.8 μs for C2H5O. The quenching rate constants by the parent molecules show a little increase with the levels of the CO stretching vibrational mode. The vibrational distribution in the photofragments is discussed using statistical models.

Intersystem crossing to the lowest triplet state of phenazine following singlet excitation with a picosecond pulse

Abstract The build-up of triplet—triplet absorption was measured for phenazine by the picosecond spectroscopy method. The measured rate constants for the build-up of the T 1 state are 7 × 10 and 5 × 10 10 5 −1 in iso-octane and in methanol re- spectively. The fast T 1 build-up would be due to the strong spin—orbit coupling between S 1 (nπ * ) and T 1 (ππ * ).

Photoelectron spectra from some autoionizing states of O2 near the ionization threshold

The photoionization efficiency curve of O2 and the vibrational distributions of photoelectrons from seven autoionizing states in the region of 0 ∼ 1.40 eV above threshold have been obtained. The apparatus used was composed of a vacuum ultraviolet monochromator, a quadrupole mass spectrometer, and a retarding‐field electron‐energy analyzer. The vibrational distributions of photoelectrons from autoionizing states were clearly different from those of calculated Franck‐Condon factors for the direct ionizing transition. The classification of the autoionizing states in this region is incomplete as yet; thus, that of Price and Collins was employed in calculation of Franck‐Condon factors for the autoionizing transitions. By comparison of the observations with the calculations the optimum values of internuclear spacing, re of the H, H′, and M progressions were determined to be 1.33 ± 0.01, 1.32 ± 0.01, and 1.28 ± 0.01 A, respectively. The re value of the M progression significantly deviated from the calculated val...

Emission spectrum of CH3S radical

The emission spectrum of the CH3S radical is obtained in the photolysis of CH3SCH3 by using a xenon resonance lamp. The emission is also obtained in the photolysis of CH3SSCH3 at ca. 200 nm irradiation as well as at 147.0 nm irradiation. The excitation threshold to produce CH3S fluorescence in the photolysis of CH3SSCH3 is determined to be 202 ± 3 nm or 6.14 ± 0.09 eV. The ratios of electronic quenching rate to fluorescence rate of CH3S* with N2, H2, D2 and CH4 are determined.

A Spectroscopic Study of the D(0u

The D( 0 u + ) ion-pair state of I2 has been analyzed by the optical–optical double resonance (OODR) technique. In a stepwise three-photon excitation scheme, D( 0 u + )–B3Π( 0 u + )–X1 Σ g + , the D( 0 u + ) state appeared in the OODR spectrum as the vibrational progressions consisting of O, Q and S branches in accord with the rotational selection rule of Δ J = 0 and ±2 for the coherent two-photon transition from the B3Π( 0 u + ) state. The D( 0 u + )–X1 Σ g + fluorescence was resolved to determine the absolute vibrational numbering of the D( 0 u + ) state. We derived Dunham parameters effective for ν = 0 through ν = 124 which were used to construct a Rydberg–Klein–Rees (RKR) potential curve.

Electronic Quenching and the Rotational Relaxation Rate of OH*(2Σ+) Produced by the Vacuum‐Ultraviolet Photodecomposition of Water

The quenching of fluorescence and the rotational relaxation of OH radicals in the electronically excited state (2Σ+) have been measured in the presence of foreign gases such as H2, D2, N2, CO, and He. The electronically excited state (2Σ+) of OH radicals has been produced by the photodecomposition of water vapor with a 1236‐A Kr resonance line. The intensity of the fluorescence of OH*(2Σ+) has been measured in the (0, 0) band. With the collision partner H2O or CO, a single collision is enough for the electronic quenching, and for other molecules, only a few collisions are sufficient. These phenomena have been explained by the long‐range chemical force between OH*(2Σ+) and foreign gases. The rotational relaxation of OH*(2Σ+) has been measured from the intensity change of K = 20 of (0, 0) band. In OH–diatomic‐molecule systems, the cross section is the largest for the collisions with H2 and about the same order of magnitude for those with D2, N2, and CO. This can be explained by the simple classical model.

Direct measurement of proton dissociation in thhe excited state of protonated 1-aminopyrene with picosecond pulses

Abstract Direct measurement of proton dissociation in the excited singlet state of protonated I-aminopyrene in a mixture of H 2 O (or D 2 O) and acetonitrile (1:1) has been carried out by means of picosecond time-resolved spectroscopy. The proton dissociation retes k 1 1 and k D+ 1 at about 300 K were determined tobe 3.7 (±0.6) * 10 9 s -1 , respectively. These rates are in very good agreement with those obtained by nanosecond time-resolved spectroscopy with fluorometry. The excited singlet state ;K * 2 value of l-aminopyrene was also determined by dynamic analyses.