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The photoabsorption and fluorescence excitation of Br2 have been investigated in the wavelength region 116–170 nm. The fluorescence lifetimes of some Rydberg excited states were measured. Perturbations in the excited states are discussed based on the comparison of the absorption and the excitation spectra. [ABSTRACT FROM AUTHOR]

The photoabsorption and fluorescence cross sections of HBr were measured in the 105–235 nm region using synchrotron radiation as a light source. Sharp absorption bands were observed in the 105–120 nm region. These bands were classified into Rydberg series, and their oscillator strengths were measured. Fluorescence in the ultraviolet region was observed and used to identify the V 1∑+ state. [ABSTRACT FROM AUTHOR]

The photoabsorption and fluorescence cross sections of HCl were measured in the 106–185 nm region. Sharp absortion 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. [ABSTRACT FROM AUTHOR]

The photoabsorption of SO was investigated by producing the radicals from a pulsed discharge of a trace of SO2 in Ar. The photoabsorption cross section of SO in the 115–135 nm region was measured. A repulsive potential curve is constructed from the observed photoabsorption spectrum. [ABSTRACT FROM AUTHOR]

The laser-induced fluorescence technique has been employed to study the first excited electronic state A 2A1 of CH3O. Vibrational levels v’3 =0–7 of the A state were excited and fluorescence decay rates were measured. Compared to a value 2.2±0.2 μs at v3=0, a significant decrease of decay rate was found at 277.6 nm (0.89 μs, v’3=7). Excitation to higher levels further reduced the lifetime. The predissociation threshold was estimated to be slightly above 276 nm (36 220 cm-1). The electronic quenching rates of the A state (v’=0–2) by CH3OH, O2, NO2, and N2 have also been determined and are compared with those of OH in the A state. [ABSTRACT FROM AUTHOR]

The vacuum ultraviolet fluorescence of Br atoms resulting from photodissociation of HBr was observed using both synchrotron radiation and argon discharge lamp as light sources. The fluorescence spectrum in the 150–165 nm region was dispersed and identified. Both the absorption and fluorescence cross sections were measured in the excitation wavelength region of 105.6–109 nm. The upper limit of HBr dissociation energy is determined to be 3.65±0.03 eV. [ABSTRACT FROM AUTHOR]

An in-house developed mobile and portable threedimensional scanning lidar system is discussed in this work. The system uses a stimulated Raman-scattering technique for the continuous observation of atmospheric aerosols, clouds and trace gases. This system has a fast scanning technique with a high-speed data acquisition, and permits the real-time measurement of atmospheric pollutants with the temporal resolution of 1 min. This scanning lidar system provides typical horizontal coverage of about 8–10 km while scanning; however, in zenith mode, good quality backscattered signals can be from 20 km, depending upon the laser power and sky conditions. This versatile lidar system has also overcome the drawbacks which are popular in the traditional scanning lidar systems such as complicated operation, overlap height between laser beam and telescope field of view In this system, the optical damage is reduced by using an integral coaxial transmitter and receiver. Some of the initial results obtained from the scanning lidar system are also presented. This study shows that boundary-layer structure and land–sea breeze circulation can be resolved from the developed scanning lidar system. The application of this lidar system to measure the pollutants over an industrial area is also discussed. [ABSTRACT FROM AUTHOR]

The electronic quenching rates of NO(A2Σ+, v′=0–2) are measured for the gases He, Ar, Xe, N2, O2, CO2, N2O, and SF6. The variations of the fluorescence intensity were measured for the (0,0), (1,0), and (2,0) bands of the γ band system when the quencher gases were added. The quenching rates were determined by using the Stern–Volmer plots with the known radiative lifetimes of the excited states. The electronic quenching rate constants are fast for the group of gases of O2, CO2, N2O, and SF6, whose quenching rate constants are in the order of 10−10 cm3/s. The quenching rate constants are slow for the group of gases including He, Ar, Xe, and N2 whose rate constants are in the order of 10−14 cm3/s. For the slow group, the quenching rate constants increase rapidly for v′=2 compared with those of v′=0 and 1. The charge transfer model and collision complex model are used to understand the quenching mechanism. For the fast group which mainly consists of gases with positive electron affinities, the charge transfer model adequately describes the mechanism. For the slow quenching group, a theoretical background is provided by consider the coupling of initial and final states in the complex potential surfaces. [Copyright &y& Elsevier]

The production of O([sup 1]D) from O[sub 2] by photodissociation was measured in the 105-113 nm wavelength region. The quantum yields of O([sup 1]D) were employed to identify the excited states as [sup 3]Σ[sub u][sup -] or [sup 3]Π[sub u], where the former correlated with the production of O([sup 1]D) and the latter production of O([sup 3]P) only. Many bands of E, E[sup ′] of [sup 3]Σ[sub u][sup -] and F, F[sup ′] [sup 3]Π[sub u], were found with their vibrational states identified. Several bands had mixed states, such as the (0,0) and (1,0) bands of D[sup ′] [sup 3]Σ[sub u][sup -]←X [sup 3]Σ[sub g][sup -] transition which had smaller than unity quantum yields of O([sup 1]D) due to the perturbation caused by the nearby states D[sup ′] [sup 3]Σ[sub u][sup +](v[sup ′]=1,2) at 112.0 and 110.0 nm. The bands of npσ[sub u] [sup 3]Π[sub u] state in the region of 105-110 nm are in agreement with the assignments of other works, and a band near 107.3 nm is consistent with the predicted band position of the F [sup 3]Π[sub u](v[sup ′]=6) upper-state. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The metastable O([sup 1]D) atom produced in the photodissociation of O[sub 2] in the wavelength region 113-130 nm was detected by measuring the 762 nm fluorescence of the transition O[sub 2](b [sup 1]Σ[sub g][sup +]→X [sup 3]Σ[sub g][sup -]). The excited states of O[sub 2] were classified as either the [sup 3]Σ[sub u][sup -] state that produces O([sup 1]D)+O([sup 3]P), or the [sup 3]Π[sub u] state that produces O([sup 3]P)+O([sup 3]P). Our quantum yield measurements of O([sup 1]D) found bands of both pure and overlapped [sup 3]Σ[sub u][sup -] and [sup 3]Π[sub u] states. Five bands were found to produce O([sup 1]D), including the longest, second, and third bands and two additional bands near 115.3 and 113.8 nm that were assigned as the E [sup 3]Σ[sub u][sup -](v[sup ′]=3-4) states. Three bands were assigned to the F [sup 3]Π[sub u](v[sup ′]=0-2) state. We also found a state at 116.2 nm, which did not produce O([sup 1]D), but produced weak visible fluorescence. The possibility of attributing the fluorescence to a transition D [sup 3]Σ[sub u][sup +]-C [sup 3]Π[sub g] was discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]