The time-dependent quantum wave packet approach has been improved and formulated to treat the multiple surface problems and thus provided a new simple, yet a clear quantum picture for interpreting the reaction mechanism underlying the nonadiabatic dynamical processes. The method keeps the salient feature of the original quantum wave packet theory developed for single surface problems, i.e. the introduction of the absorbing potential and the grid basis including the discrete variable representation and the fast Fourier transformation, which makes the present methodology a very efficient implement for the nonadiabatic quantum scattering calculations. Here, we review the theoretical basis of this approach and its applications to the fundamental triatomic chemical reactions, the latter include the nonadiabatic dynamics calculations on the F + H2, F + HD, F + D2, O(1D) + N2, O(3P, 1D) + H2, D+ + H2, and H+ + D2 reactions. We also present a thorough historical overview of the theoretically nonadiabatic dynamica...

The time-dependent quantum wave packet approach to the electronically nonadiabatic processes in chemical reactions

The near-ultraviolet (UV) photochemistry of ozone remains a topic of great contemporary interest. Figure 1 shows the absorption spectrum of ozone in the UV region between 195 and 345 nm at 295 K, which is plotted using the data measured by Malicet et al.1 The UV absorption spectrum of O3 consists of two bands. The wide bell-shaped absorption peaking at approximately 250 nm is called the Hartley band. The vibrational structure in the long wavelength edge of Hartley band in the 310-360 nm region is called the Huggins band. Table 1 lists the threshold wavelengths for the dissociation processes to various * To whom correspondence should be addressed. Fax: +81-53389-5593. E-mail: matsumi@stelab.nagoya-u.ac.jp. Yutaka Matsumi earned his doctorate degree in Chemistry at Tokyo Institute of Technology in 1981. After he spent several years in private companies, he was an associate professor at Hokkaido University for nine years. He has been at the Solar-Terrestrial Environment Laboratory at Nagoya University since 1997. His research interests include chemical reaction processes in the atmosphere and development of instruments for atmospheric gases and particles.

Photolysis of atmospheric ozone in the ultraviolet region.

Hot oxygen and carbon escape from the martian atmosphere

A laser flash photolysis–laser-induced fluorescence (LIF) technique has been used to study the kinetics of the reactions of electronically excited oxygen atoms, O(1D2), with N2, O2, N2O, CH4, H2, CO2, Ar, Kr and n-C4H10 over the temperature range 195–673 K. The majority of studies employed direct detection of O(1D2) atoms using vacuum ultraviolet LIF at 115.2 nm, whereas some studies employed LIF detection of OH generated from reaction of O(1D2) with a H atom donor species as a marker for O(1D2). The bimolecular rate coefficient for reaction with N2
				(kN2) is well described by the Arrhenius expression kN2 = (2.2 ± 0.3) × 10−11exp{(118 ± 21)/T}
				(95% confidence level), in good agreement with two other new studies reported in this issue, but giving significantly higher values of kN2 than previously measured, with important implications for production rates of OH and NO radicals in the atmosphere. At 295 K the following rate coefficients were obtained (in units of cm3 molecule−1 s−1, 95% confidence level including estimated systematic errors): kN2 = (3.06 ± 0.25) × 10−11, kO2 = (3.8 ± 0.4) × 10−11, kN2O = (1.07 ± 0.1) × 10−10, kCH4 = (1.4 ± 0.2) × 10−10, kH2 = (1.5 ± 0.1) × 10−10, kCO2 = (1.4 ± 0.1) × 10−10, kAr = (8 ± 3) × 10−13, kKr = (9 ± 1) × 10−12 and kn-C4H10 = (4.55 ± 0.2) × 10−10, in good agreement with the new studies reported in this issue, and with previous measurements, where available. An analysis of the correlation between the cross-section for O(1D2) removal and the ionisation potential of the collision partner suggests at least two mechanisms operate for the removal of O(1D2).

Laser induced fluorescence studies of the reactions of O(1D2) with N2, O2, N2O, CH4, H2, CO2, Ar, Kr and n-C4H10

[1] Atmospheric nitrous oxide (N2O) is enriched in heavy oxygen and nitrogen isotopes relative to its tropospheric sources. This enrichment is traced back to kinetic isotope effects in the two stratospheric N2O sink mechanisms, i.e., photolysis and reaction with O(1D). Most of the previous studies on the cause of isotopic enrichment in N2O have focused on photolysis. Here we present results on the 18O and the position-resolved 15N kinetic isotope effects in the reaction of nitrous oxide with O(1D) obtained by recently developed mass spectrometric techniques. Just as in the photolysis sink, a heavy isotope enrichment in the residual N2O was found, but of smaller magnitude. However, the fractionation pattern of nitrogen isotopes at the two nonequivalent positions in the molecule is clearly distinct from that in photolytic N2O destruction. The fractionation constant for the terminal nitrogen atom, 15e1 = k(14N2O)/k(15N14NO) − 1 = (8.87 ± 0.15) %, is larger than for the central nitrogen atom, 15e2 = k(14N2O)/k(14N15NO) − 1 = (2.22 ± 0.12) % (all errors are 2σ). The fractionation constant for oxygen, 18e = k(N216O)/k(N218O) − 1 = (12.38 ± 0.14) %, was found to be larger than for nitrogen and amounts to about twice the value from the single previous determination. The larger influence of the O(1D) sink at lower stratospheric altitudes could probably explain the lower ratio of 15e2/15e1 (≡η) observed there, which is shown to be only marginally influenced by transport. The published data on stratospheric η values suggest that, if there are no other chemical reactions involved, up to 60% of the overall N2O loss at lower altitudes could be from the reaction with O(1D).

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JD001506

Intramolecular 15N and 18O fractionation in the reaction of N2O with O(1D) and its implications for the stratospheric N2O isotope signature

Translational relaxation and electronic quenching processes of translationally hot O(1D) atoms by collisions with N2 in a gas cell at room temperature are studied using a vacuum ultraviolet laser induced fluorescence technique. The initial hot O(1D) atoms which have translational energies of 18.2 and 9.8 kcal mol−1 are produced by the photodissociation of N2O at 193 nm and O2 at 157 nm, respectively. The translational relaxation processes are investigated by time resolved measurements of the Doppler profiles for the O(1D) atoms, while the quenching processes are studied by measuring both the decrease of the O(1D) concentration and the increase of the product O(3P) concentration after the photochemical formation of the hot O(1D) atoms. When the initial translational energy of O(1D) is 9.8 kcal mol−1, about 40% of the O(1D) atoms are electronically quenched before the entire thermalization of the hot O(1D) atoms takes place in a gaseous mixture with N2. This indicates that the translational relaxation rate ...

Translational relaxation and electronic quenching of hot O(1D) by collisions with N2

O atoms in the 3P2 state were detected by vacuum ultraviolet laser-induced fluorescence (VUV LIF) technique. The O(3P2) atoms were produced by the collision between the O atoms in the 1D excited state and collision partner N2. O atoms in the 1D excited state were obtained by photodissociation of N2O at 193 nm laser light. As O(3P2) species has their first transition in the VUV region, the probe laser was used to excite O(2p3Pj) atoms to the O(3s3So) state at 130.212 nm. A four wave difference frequency mixing (2ω1−ω2) process using Kr as nonlinear media was employed to generate 130.212 nm probe laser light.

A. M. Sarwaruddin Chowdhury

Papers

Translational relaxation and electronic quenching of hot O(1D) by collisions with N2

Detection of o(3p2) by vacuum ultraviolet laser spectroscopy