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Suto, M.

Publications and source records attributed to Suto, M..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

OH(A-X) fluorescence from photodissociative excitation of HO2 at 157.5 nm

The OH(A-X) fluorescence from photodissociative excitation of HO2 by F2 laser photons (157.5 nm) was observed and compared with the OH fluorescence spectra of H2O2 and the O2+CH3OH mixture. The rotational population distributions of OH(A) were obtained from the fluorescence spectra. The most populated levels are J = 4 for photodissociative excitation of HO2, J = 20 for H2O2, and J = 21 for the O2+CH3OH mixture. The fluorescence from the gas mixture is attributed to the O + H recombination for which the atoms are produced from photodissociation of parent molecules.

Suto, M.↗
NASA NTRS1986

Quantitative photoabsorption and fluorescence study of HCl in vacuum ultraviolet

The photoabsorption and fluorescence cross sections of HCl were measured in the 106-185 nm region. Sharp absorption bands appear at wavelengths shorter than 135 nm, and fluorescence occurs at several excited states. The fluorescence cross sections are generally quite small, indicating that the excited states are strongly predissociative. The molecular processes for producing the VUV and UV fluorescences are investigated, and the Rydberg characteristics of the strong absorption bands are discussed.

Nee, J. B.↗
NASA NTRS1986

Quantitative VUV spectroscopy of Cl2

The photoabsorption and fluorescence cross sections of Cl2 were measured in the 105-145 nm region using synchrotron radiation as a light source. The oscillator strengths for the major absorption bands were calculated from the measured absorption cross sections. The measured oscillator strengths for the 2 3Pi u and 2 1Pi u - X 1Sigma(+)g transitions agree quite well with the theoretical values. The absorption spectrum was analyzed in accord with the excited electronic states calculated by Peyerimhoff and Buenker (1981). The Rydberg series converging to the first and second ionization potentials were classified. The vibrational levels of the 2 1Sigma(+)u ionic state were determined up to v prime = 15 from the fluorescence excitation spectrum. It was observed that a band with peak at 108.3 nm produces VUV fluorescence, but it produces UV fluorescence only by a collisional excitation process.

Lee, L. C.↗
NASA NTRS1986

Measurements of HO2 chemical kinetics with a new detection method

Research for the period from December 1, 1985 to May 31, 1986 is discussed, i.e., the reaction rate constant of HO2+O3 has been measured with a discharge-flow-tube apparatus. The HO2 radical was detected by the OH(A-X) photofragment emission produced from photodissociative excitation of HO2 at 147 nm. In the meantime, the optical emissions produced by the vacuum ultraviolet excitation of chemical species in the flow tube were investigated and used to examine the possibility for their interference with the HO2 detection. The research results are summarized below.

Lee, L. C.↗
NASA NTRS1985

Photoabsorption cross section of CH3CN - Photodissociation rates by solar flux and interstellar radiation

The photoabsorption cross section of CH2CN vapor was measured in the 106-180 nm region using synchrotron radiation as a light source. The cross section and the quantum yield for the production of CN (A, B-X) fluorescence were measured and were used to infer the photodissociation cross section of CH3CN. The cross sections were used to calculate the photodissociation rates of CH3CN by the solar flux and by the interstellar radiation. In both the stratosphere and the troposphere, the solar photodissociation of CH3CN is negligible in comparison with chemical degradation.

Suto, M.↗
NASA NTRS1984

Quantitative photoexcitation and fluorescence studies of C2H2 in vacuum ultraviolet

Synchrotron radiation light source measurements were conducted in the 105-155 nm region to obtain the photoabsorption and fluorescence cross sections of C2H2, and the quantum yield for producing the C2H-asterisk fluorescence from C2H2's photodissociation was measured in the 106-136.5 nm region. The products of the radiative lifetime quenching rate constant increase with excitation wavelengths. The data obtained on lifetimes, quenchings, and fluorescence spectra point to an upper state of the C2H-asterisk fluorescence that is well bound, while the lower state is a repulsive or weak-bound state.

Suto, M.↗
NASA NTRS1983

Photodissociation of NH3 at 106-200 nm

The absorption and fluorescence cross sections for NH3 are measured in the 106-200 nm region using synchrotron radiation as the light source. The threshold wavelengths for the production of the NH (b to X) and NH (c to a) emissions from NH3 dissociation are measured and compared with previous measurements. The heat of formation of NH determined from these thresholds agrees well with the value determined from thermochemical data. The process of dissociation of NH3 into NH2(2AL) and H2(S) has a significant quantum yield whose maximum at 134 nm is about twice the NH(c) production yield. All the vibronic levels of the B and C states produce the NH2(2A1) emission, contrary to previous theoretical interpretations.

Suto, M.↗
NASA NTRS1982

Photodissociation yields of CS2 at 1060-1520 A

Photoabsorption and fluorescence cross sections of CS2 were measured in the 1060-1520 A region using synchrotron radiation in order to provide information needed for modeling the CS abundance in the interstellar medium. The absorption in the 1060-1200 A region is smooth and continuous, except for the presence of a strong absorption band at 1117 A, while for wavelengths longer than 1200 A, the absorption spectrum shows the structure of Rydberg states. The fluorescence in the 1900-3000 A region begins to appear at 1335 A, and is mainly the CS(A 1Pi-Chi 1Sigma +) transition in the 2400-2800 A region. The fluorescence in the 1900-8000 A region begins to appear at 1490 A, and, in addition to the previous transition, is composed of the transitions of S(1S0-3P1) at 4589 A and of CS(d 3 Delta, a-prime 3Sigma +, and a 3Pi-Chi 1Sigma +) at 3000-4000 A. The quantum yields for the production of fluorescence are determined to have maxima of 13 and 7.5% at 1235 A for the fluorescence in the 1900-8000 and 1900-3000 A regions, respectively.

Day, R. L.↗
NASA NTRS1982

Fluorescence yields from photodissociation of SO2 at 1060-1330 A

The absorption and fluorescence cross sections of SO2 were measured in the 1060-1330 A region using synchrotron radiation as the light source. Several absorption bands were observed and assigned tentatively to the Rydberg states converging to the SO2(+) states. It is shown that the apparent quantum yields for excitation wavelengths longer than 1200 A are small, and are presumably emitted from the O(1S) and S(1S) metastable species. At shorter excitation wavelengths, the fluorescence cross sections increase at the threshold wavelengths of possible SO2 dissociation processes.

Suto, M.↗