Observation of Partial Wave Resonances in Low-Energy O2–H2 Inelastic Collisions

Science ◽  
2013 ◽  
Vol 341 (6150) ◽  
pp. 1094-1096 ◽  
Author(s):  
Simon Chefdeville ◽  
Yulia Kalugina ◽  
Sebastiaan Y. T. van de Meerakker ◽  
Christian Naulin ◽  
François Lique ◽  
...  
Keyword(s):  
Partial Wave ◽  
Cross Sections ◽  
Ground State ◽  
Total Angular Momentum ◽  
Inelastic Collisions ◽  
Quantum Mechanical ◽  
Quantum Scattering ◽  
Rotational Excitation ◽  
Collision Processes ◽  
Theoretical Results

Partial wave resonances predicted to occur in bimolecular collision processes have proven challenging to observe experimentally. Here, we report crossed-beam experiments and quantum-scattering calculations on inelastic collisions between ground-state O2 and H2 molecules that provide state-to-state cross sections for rotational excitation of O2 (rotational state N = 1, j = 0) to O2 (N = 1, j = 1) in the vicinity of the thermodynamic threshold at 3.96 centimeter−1. The close agreement between experimental and theoretical results confirms the classically forbidden character of this collision-induced transition, which occurs exclusively in a purely quantum mechanical regime via shape and Feshbach resonances arising from partial waves with total angular momentum (J) = 2 to 4.

Seemingly Anomalous Angular Distributions in H + D2 Reactive Scattering

Science ◽  
2012 ◽  
Vol 336 (6089) ◽  
pp. 1687-1690 ◽  
Author(s):  
Justin Jankunas ◽  
Richard N. Zare ◽  
Foudhil Bouakline ◽  
Stuart C. Althorpe ◽  
Diego Herráez-Aguilar ◽  
...  
Keyword(s):  
Cross Sections ◽  
Collision Energy ◽  
Minimum Energy ◽  
Angular Distributions ◽  
Quantum Mechanical ◽  
Minimum Energy Path ◽  
Reactive Scattering ◽  
Rotational Excitation ◽  
Reaction Products ◽  
Trajectory Calculations

When a hydrogen (H) atom approaches a deuterium (D2) molecule, the minimum-energy path is for the three nuclei to line up. Consequently, nearly collinear collisions cause HD reaction products to be backscattered with low rotational excitation, whereas more glancing collisions yield sideways-scattered HD products with higher rotational excitation. Here we report that measured cross sections for the H + D2 → HD(v′ = 4, j′) + D reaction at a collision energy of 1.97 electron volts contradict this behavior. The anomalous angular distributions match closely fully quantum mechanical calculations, and for the most part quasiclassical trajectory calculations. As the energy available in product recoil is reduced, a rotational barrier to reaction cuts off contributions from glancing collisions, causing high-j′ HD products to become backward scattered.

Inelastic collisions between excited alkali atoms and molecules. V. Sensitized fluorescence in mixtures of sodium with N2, H2, HD, and D2

1968 ◽  
Vol 46 (19) ◽  
pp. 2127-2131 ◽  
Author(s):  
M. Stupavsky ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Resonance Effect ◽  
Excitation Transfer ◽  
Inelastic Collisions ◽  
Sodium Vapor ◽  
Sensitized Fluorescence ◽  
Atoms And Molecules ◽  
Alkali Atoms ◽  
Exciting Beam

3 2P1/2 ↔ 3 2P3/2 excitation transfer in sodium, induced in inelastic collisions with ground-state N2, H2, HD, and D2 molecules, has been investigated in a series of sensitized fluorescence experiments. Mixtures of sodium vapor at a pressure of 5 × 10−7 Torr, and the gases, were irradiated with each NaD component in turn, and the fluorescence which contained both D components was monitored at right angles to the direction of the exciting beam. Measurements of the relative intensities of the NaD fluorescent components yielded the following collision cross sections for excitation transfer. For Na–N2 collisions: Q12(2P1/2 → P3/2) = 144 Å2, Q21(2P1,2 ← 2P3/2) = 76 Å2 for Na–H2 collisions: Q12 = 80 Å2, Q21 = 42 Å2. For Na–HD collisions: Q12 = 84 Å2, Q21 = 44 Å2. For Na–D2 collisions: Q12 = 98 Å2, Q21 = 52 Å2. The cross sections Q21 exhibit a slight resonance effect between the atomic and molecular rotational transitions.

scholarly journals Thermal Inelastic Collision Processes

1958 ◽  
Vol 8 ◽  
pp. 979-991
Author(s):  
M. J. Seaton
Keyword(s):  
Cross Sections ◽  
Inelastic Collision ◽  
Heavy Particle ◽  
Inelastic Collisions ◽  
Impact Excitation ◽  
Semiempirical Methods ◽  
Particle Collisions ◽  
Exchange Reactions ◽  
Proton Impact ◽  
Collision Processes

Section II contains a summary of relevant collision theory methods. Section III is concerned with heavy particle collisions: excitation of H 1s hyperfine structure (hfs) states by H atom impact; excitation of H2 rotation by H and H2 impact; H 2s→2p transitions produced by proton impact; charge exchange reactions; excitation of atomic levels by proton impact. Section IV deals with inelastic collisions between atoms and electrons. Use of the Born and distorted wave approximations is discussed. Calculations of cross sections for excitation of forbidden lines in pq configurations are reviewed and new results presented for O+2, N+, C+, and Si+, both variational and semiempirical methods being used. In Sec. V, concerned with atomic photoionization, new results are given for photoionization from 2pq configurations.

Inelastic Collisions between Excited Alkali Atoms and Molecules. VIII. 62P1/2–62P3/2 Mixing and Quenching in Mixtures of Rubidium with H2, HD, D2, N2, CH4, and CD4

1973 ◽  
Vol 51 (3) ◽  
pp. 257-265 ◽  
Author(s):  
I. N. Siara ◽  
L. Krause
Keyword(s):  
Fine Structure ◽  
Cross Sections ◽  
Ground State ◽  
Inelastic Collisions ◽  
Fluorescent Intensity ◽  
Rubidium Vapor ◽  
Sensitized Fluorescence ◽  
Molecular Gases ◽  
Alkali Atoms ◽  
Intensity Ratios

Excitation transfer between the 62P fine-structure substates in rubidium, induced in inelastic collisions with ground-state molecules, has been studied using techniques of sensitized fluorescence. Rubidium vapor in mixtures with various molecular gases was irradiated with each component of the 2P rubidium doublet in turn, and measurements of sensitized-to-resonance fluorescent intensity ratios yielded the following mixing cross sections Q12(2P1/2 → 2P3/2) and Q21(2P1/2 ← 2P3/2), as well as effective quenching cross sections Q1X(2P1/2 → 2XJ″) and Q2X(2P3/2 → 2XJ″). For collisions with H2: Q12(2P1/2 → 2P3/2) = (41 ± 5) Å2; Q21(2P1/2 ← 2P3/2) = (26 ± 3) Å2; Q1X(2P1/2 → 2XJ″) = (36 ± 9) Å2; Q2X(2P3/2 → 2XJ″) = (31 ± 8) Å2. For HD: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (47 ± 13) Å2; Q2X = (38 ± 10) Å2. For D2: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (28 ± 8) Å2; Q2X = (21 ± 7) Å2. For N2: Q12 = (107 ± 15) Å2; Q21 = (70 ± 10) Å2; Q1X = (128 ± 44) Å2; Q2X = (126 ± 33) Å2. For CH4: Q12 = (38 ± 6) Å2; Q21 = (24 ± 3) Å2; Q1X = (129 ± 41) Å2; Q2X = (114 ± 37) Å2. For CD4: Q12 = (52 ± 7) Å2; Q21 = (34 ± 5) Å2; Q1X = (82 ± 30) Å2; Q2X = (76 ± 22) Å2. An analysis of these results suggests the possibility of resonances with various molecular rotational and vibrational transitions.

scholarly journals State-Selective Electron Capture Cross Sections in Collision Between Be4+ and Ground State Hydrogen Atom – Significant Improvement in the Classical Treatment

2021 ◽  
Author(s):  
Iman Ziaeian ◽  
Károly Tőkési
Keyword(s):  
Hydrogen Atom ◽  
Electron Capture ◽  
Cross Sections ◽  
Ground State ◽  
Correction Term ◽  
Projectile Energy ◽  
Quantum Mechanical ◽  
Capture Cross ◽  
Mechanical Methods ◽  
Capture Cross Sections

Abstract We present state-selective electron capture cross sections in collision between Be4+ and ground state hydrogen atom. The n- and nl-selective electron capture cross sections are calculated by a three-body classical trajectory Monte Carlo method (CTMC) and by a classical simulation schema mimicking quantum features of the collision system. The quantum behavior is taken into account with the correction term in the Hamiltonian as was proposed by Kirschbaum and Wilets (C. L. Kirschbaun, and L. Wilet, Phys. Rev. A 21, 834 (1980)). Calculations are carried out in the projectile energy range of 1-1000 keV/amu. We found that our model for Be4++ H(1s) system remarkably improves the obtained state-selective electron capture cross sections, especially at lower projectile energies. Our results are very close and are in good agreement with the previously obtained quantum-mechanical results. Moreover our model with simplicity can time efficiently carry out simulations where maybe the quantum mechanical ones become complicated, therefore, our model should be an alternative way to calculate accurate cross sections and maybe can replace the quantum-mechanical methods.

K-shell photoionization of Be-like nitrogen from the ground state: energies and Auger widths of the high-lying double-excited states for N IV

2018 ◽  
Vol 96 (11) ◽  
pp. 1183-1191
Author(s):  
Liang Liang ◽  
Chao Zhou
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Photoionization Cross Section ◽  
Coupling Scheme ◽  
Close Coupling ◽  
Resonance Energies ◽  
Auger Spectra ◽  
Distorted Wave Method ◽  
Theoretical Results ◽  
Good Agreement

The K-shell photoionization cross section of Be-like nitrogen (N IV) from the ground state is studied with the R-matrix and distorted-wave method for photon energies from 5.7 to 41.2 Ry. The close-coupling expansion includes 34 target states of N V with the 13 configurations in the LS-coupling scheme. The resonance energies, quantum defect and widths of 18 series of autoionization are determined from QB method and agree with these by cross sections. Our theoretical resonance energies and widths are compared with the existing experiments on the Auger spectra and other theoretical results. The results show that the calculated resonance energies are in rather good agreement with the experiment on the Auger spectra. For the autoionization width of some resonance states, good agreement is also found with recent theoretical results wherever available obtained using a saddle-point complex-rotation method.

Sensitized Fluorescence in Sodium Induced in Collisions with Hg(63P1) Atoms

1973 ◽  
Vol 51 (3) ◽  
pp. 334-342 ◽  
Author(s):  
M. Czajkowski ◽  
G. Skardis ◽  
L. Krause
Keyword(s):  
Excitation Energy ◽  
Cross Sections ◽  
Ground State ◽  
Absolute Intensity ◽  
Resonance Radiation ◽  
Inelastic Collisions ◽  
Sensitized Fluorescence ◽  
Subsequent Decay ◽  
Intensity Measurements ◽  
Fluorescent Spectrum

Collisional transfer of excitation from mercury to sodium was investigated using methods of sensitized fluorescence. A mixture of mercury and sodium vapors at low pressure was irradiated with Hg 2537 Å resonance radiation, producing a population of Hg(63P1) atoms whose inelastic collisions with ground-state sodium atoms resulted in a transfer of excitation energy to close-lying S, P, and D states in sodium. The subsequent decay of these states manifested itself in the emission of a sensitized fluorescent spectrum. Absolute intensity measurements on the components of the spectrum yielded 21 cross sections whose magnitudes range from 0.02 to 38.5 Å2 and which exhibit a pronounced resonance with ΔE, the energy defect between Hg (63P1) and the appropriate level in sodium.

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