Reaction of Metastable Ar*(³P₂) and Kr*(³P₂) Atoms with Water Vapor:  Excitation Functions for Electronic Quenching Collisions

Abstract

In this paper, we examine the functional nature of the state-specific cross section for electronic quenching σQ(E) in collisions of metastable noble gas atoms [Ar*(3P2) and Kr*(3P2)] with ground-state water molecules confined to a scattering-gas cell. The relative kinetic energy range studied is E = 0.0463−0.772 eV for Ar*(3P2) and 0.0432−0.692 eV for Kr*(3P2). These beam-gas-luminescence experiments incorporate a novel state-specific monitor system employing Xe gas. Photon emission from a state-specific Xe state produced in quenching collisions with the respective metastable noble gas (Ng*) atoms is a direct measure of the total disappearance of the metastable state under scrutiny in the reaction with water vapor. We use the classical orbiting and absorbing sphere models with empirically derived parameters [London dispersion C disp, induction C ind (spherically averaged or aligned dipole), and absorbing sphere radius r as] to predict energy-dependent cross sections for the total quenching reactions. The underlying premise of the models is that although the quenching process itself is envisioned to be a short-range two-electron exchange interaction, it is the long-range attractive forces between the respective collision partners that are critical in determining whether such short-range processes ultimately occur. Values of σ Q determined from the models are in very good agreement with our experiment. This work supersedes our previous study for Ar*(3P2,0) [Novicki, S.; Krenos, J. J. Chem. Phys. 1988, 89, 7031].

Gas temperature, electron density and electron temperature measurement in a microwave excited microplasma

“…Another assumption made in the model is that the kinetics is not affected by the presence of H 2 O (less than 100 ppm in the experiment). Even though the presence of some molecules, such as O 2 , CO 2 and H 2 O, may be important to argon kinetics due to the strong energy-transfer process [31,32], it is found that the argon kinetics is not affected significantly unless the H 2 O concentration is larger than 1000 ppm.…”

“…Here σ is the cross section, r 0 and E H ion are the first Bohr radius and the ionization energy of hydrogen; E is the kinetic energy of the particles (electron or atom) and E th is the threshold energy; G is a function corresponding to a specific process; parameter f is the oscillator strength between two levels (before and after collisions) while α and α 0 are constants which can be adjusted according to the experimentally measured or theoretically calculated cross sections [15,16]. The cross section set in [15,16] is updated according to the recent works, for electron-atom collisions [25][26][27][28][29][30] and atom-atom collisions [31,32]. Einstein coefficients (A i→j ) are from [28].…”

Biointeractions of Herbicide Atrazine with Human Serum Albumin: UV-Vis, Fluorescence and Circular Dichroism Approaches

“…The K q ranges from 6.66 × 10 12 to 8.90 × 10 12 mol/L at an excitation wavelength of 280 nm, and when the excitation wavelength set to 295 nm, the value of K q ranges from 6.07 × 10 12 to 8.12 × 10 12 mol/L. It is apparent from the data that the quenching constants at different excitation wavelengths are very close, indicating that ATR mainly quenches the fluorescence of Trp residues and is more than 100 times the maximum dispersion collision quenching constant (2.0 × 10 10 mol/L) [ 39 , 40 ] of the various quenchers and biological macromolecules. Therefore, this reaction produces a complex of ATR and HSA, and the endogenous fluorescence of HSA is quenched via the static quenching mechanism.…”

Atmospheric‐pressure Penning ionization mass spectrometry

“…In addition to reactions (3) to (5), the annihilation of Rg* due to the presence of impurities may also play a role. For example, the rate constant for reaction (6) was measured to be 8.1 × 10 −10 cm 3 s −1 ,13 and only a 40 ppb level of H 2 O impurity in the atmospheric‐pressure Ar reagent gas leads to the decay lifetime of Ar* ( τ = ln2/ k [H 2 O]) being 1 ms. Thus it is highly desirable to use high‐purity reagent rare gas.…”