Molecular Beam Measurements of the Rotational State Distribution of RbBr Produced in Reactive Scattering of Rb on Br2

1970 ◽  
Vol 53 (8) ◽  
pp. 3376-3378 ◽  
Author(s):  
R. Grice ◽  
J. E. Mosch ◽  
S. A. Safron ◽  
J. P. Toennies
Keyword(s):  
Molecular Beam ◽  
Rotational State ◽  
Reactive Scattering ◽  
State Distribution

Fringe fields are important when examining molecular orientation in a cold ammonia beam

2021 ◽  
Author(s):  
Paul Bertier ◽  
Brianna Heazlewood
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Molecular Orientation ◽  
Molecular Beam ◽  
Buffer Gas ◽  
State Distribution ◽  
Experimental Apparatus ◽  
Set Up ◽  
A Minor ◽  
Fringe Fields

Abstract External fields have been widely adopted to control and manipulate the properties of gas-phase molecular species. In particular, electric fields have been shown to focus, filter and decelerate beams of polar molecules. While there are several well-established approaches for controlling the velocity and quantum-state distribution of reactant molecules, very few of these methods have examined the orientation of molecules in the resulting beam. Here we show that a buffer gas cell and three-bend electrostatic guide (coupled to a time-of-flight set-up) can be configured such that 70% of ammonia molecules in the cold molecular beam are oriented to an external electric field at the point of detection. With a minor alteration to the set-up, an approximately statistical distribution of molecular orientation is seen. These observations are explained by simulations of the electric field in the vicinity of the mesh separating the quadrupole guide and the repeller plate. The combined experimental apparatus therefore offers control over three key properties of a molecular beam: the rotational state distribution, the beam velocity, and the molecular orientation. Exerting this level of control over the properties of a molecular beam opens up exciting prospects for our ability to understand what role each parameter plays in reaction studies.

Crossed-beam studies of radical reaction dynamics:

1994 ◽  
Vol 72 (3) ◽  
pp. 660-672 ◽  
Author(s):  
R. Glen Macdonald ◽  
Kopin Liu Argonne ◽  
David M. Sonnenfroh ◽  
Di-Jia Liu
Keyword(s):  
Cross Sections ◽  
Molecular Beam ◽  
Radical Reaction ◽  
Reaction Cross ◽  
Translational Energy ◽  
Vibronic State ◽  
State Distribution ◽  
Title Reaction ◽  
Vibrational Ground State ◽  
Reaction Cross Sections

The title reaction has been studied in a crossed molecular beam apparatus. Both the product state distributions and the translational energy dependence of the reaction cross sections were measured under single collision conditions. Excellent agreement was found over a wide temperature range (26–3800 K) between rate constants deduced from the translational excitation function and recent thermal kinetic data. The rotational state distribution was found to be very cold compared to the reaction exothermicity, and could be described by a Boltzmann temperature of 110 K for all K-doublet levels. The vibronic state distribution was also found to be cold, with 70% of the products formed in the vibrational ground state. By comparing the molecular beam results for vibronic state distributions with those obtained from recent bulb experiments, it was conjectured that there appears to be a strong correlation between rotation in the reactants and bending excitation in the products.

scholarly journals Origin of the “odd” behavior in the ultraviolet photochemistry of ozone

2020 ◽  
Vol 117 (35) ◽  
pp. 21065-21069
Author(s):  
Shanyu Han ◽  
Carolyn E. Gunthardt ◽  
Richard Dawes ◽  
Daiqian Xie ◽  
Simon W. North ◽  
...  
Keyword(s):  
Quantum Theory ◽  
Selection Rule ◽  
Rotational Quantum Number ◽  
Rotational State ◽  
Isotopic Enrichment ◽  
State Distribution ◽  
Rotational States ◽  
Increasing Temperature ◽  
Full Quantum ◽  
Curve Crossing

The origin of the even–odd rotational state population alternation in the16O2(a1Δg) fragments resulting from the ultraviolet (UV) photodissociation of16O3, a phenomenon first observed over 30 years ago, has been elucidated using full quantum theory. The calculated16O2(a1Δg) rotational state distribution following the 266-nm photolysis of 60 K ozone shows a strong even–odd propensity, in excellent agreement with the new experimental rotational state distribution measured under the same conditions. Theory indicates that the even rotational states are significantly more populated than the adjacent odd rotational states because of a preference for the formation of the A′ Λ-doublet, which can only occupy even rotational states due to the exchange symmetry of the two bosonic16O nuclei, and thus not as a result of parity-selective curve crossing as previously proposed. For nonrotating ozone, its dissociation on the excited B1A′ state dictates that only A′ Λ-doublets are populated, due to symmetry conservation. This selection rule is relaxed for rotating parent molecules, but a preference still persists for A′ Λ-doublets. The A′′/A′ ratio increases with increasing ozone rotational quantum number, and thus with increasing temperature, explaining the previously observed temperature dependence of the even–odd population alternation. In light of these results, it is concluded that the previously proposed parity-selective curve-crossing mechanism cannot be a source of heavy isotopic enrichment in the atmosphere.

Sign in / Sign up

Export Citation Format

Share Document