Laser-induced fluorescence excitation spectroscopy of N₂ ⁺ produced by VUV photoionization of N₂ and N₂O

Abstract

Synchrotron radiation emitted from the UVSOR storage ring is monochromated by a grazing-incidence monochromator and introduced coaxially with the second harmonic of a mode-locked Ti:sapphire laser. Sample gases, N(2) and N(2)O, are photoionized into vibronically ground N(2)(+) with the fundamental light of the undulator radiation at 18.0 and 18.6 eV, respectively. Laser-induced fluorescence (LIF) excitation spectra of N(2)(+) from N(2) and N(2)O are measured in the laser wavelength region of the (B (2)Sigma(u)(+), v' = 0) <-- (X (2)Sigma(g)(+), v" = 0) transition at 389-392 nm. The LIF excitation spectra of N(2)(+) exhibit two maxima due to the P and R branches in which rotational bands are heavily overlapped. The rotational temperature is determined by simulating an LIF excitation spectrum by using the theoretical intensity distribution of rotation bands convoluted with the spectral width of the laser.

Elevated Glucose and Interleukin-1β Differentially Affect Retinal Microglial Cell Proliferation

“…Since IL-1 β is an important mediator of the inflammatory responses, and is involved in a variety of cellular processes, including cell proliferation, differentiation, and apoptosis [31, 32], we evaluated whether exposure to IL-1 β per se could increase apoptosis in retinal neural cells.…”

“…Nevertheless, in the last decade, growing evidence has shown that diabetic retinopathy has features of a low-grade chronic inflammatory disease [21]. In fact, it has been shown that microglial and macroglial cell activation is an important feature of neuroinflammation present in the diabetic retina [17, 31–34]. Moreover, increased production of inflammatory mediators, such as IL-1 β [21, 35], TNF- α [35], and NO [12, 21] has been reported in the retinas of diabetic animals.…”

Laser-Induced Fluorescence from N2+ Ions Generated by a Corona Discharge in Ambient Air

“…For example, LIF via the nitrogen first-negative B 2 Σ + u → X 2 Σ + g transition has been typically measured at pressures of order 1 Torr with the ions generated most commonly in high numbers using electric discharge, 6,7 electron beams, 8,9 and synchrotron radiation. 10 Prevalent nitrogen cation LIF has also been reported in higher pressure buffer gases, e.g., He, with ions generated using optical resonance-enhanced multi-photon ionization. 11–13 More recently, cavity ring-down absorption spectroscopy has been used for the detection of N 2 + in an atmospheric pressure nitrogen glow discharge with an estimated limit of detection of 7 × 10 10 cm −3 .…”

“…The ions were generated continuously by a plasma glow discharge in low pressure N 2 and by a corona discharge in ambient air. The fluorescence decay time was found to rapidly decrease with increasing pressure leading to an extrapolated decay rate of ≈10 10 s −1 at atmospheric pressure. In spite of this quenching, we were able to observe laser induced fluorescence in ambient air by means of a time-gated spectral measurement.…”

“…In spite of this quenching, we were able to observe laser induced fluorescence in ambient air by means of a time-gated spectral measurement. In the process of comparing the emission signal with that of N 2 spontaneous Raman scattering, ion concentrations in ambient air of order 10 8 -10 10 cm −3 were determined. With moderate increases in laser power and collection efficiency, ion concentrations of less than 10 6 cm −3 may be measurable, potentially enabling applications in atmospheric standoff detection of ionizing radiation from hazardous radioactive sources.…”