Reactive asymmetry of methyl iodide. The crossed-beam reaction of oriented methyl iodide with rubidium

Parker, David H.; Chakravorty, K. K.; Bernstein, R. B.

doi:10.1021/j150605a002

Cited by 82 publications

(29 citation statements)

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“…Taking into account that the experimental value is an average over all initial conditions (limited to j i ) 0, j i ) 1, and j i ) 2, in our case), it follows that 0 close to 150°is probably the most realistic cutoff angle. For the reaction of Ca( 1 D) with CH 3 Cl we found the same value. 28 Let us now ask the question: how are the reactive cross section and the A/B branching ratio affected by the Σ or Π polarization of the Ca( 1 P) atom?…”

Section: Resultssupporting

confidence: 74%

“…A beam of symmetric top (like) molecules can be oriented through the selection of a specific (jkm) state by means of a hexapole field. [1][2][3][4][5][6] The (partial) orientation or alignment of molecules can also be achieved by brute force methods. [7][8][9] Excited atoms have been prepared by electrical discharge 5,6,10,11 and by laser excitation; [12][13][14][15] in the latter case one can select specifically aligned substates by an appropriate choice of the laser polarization.…”

Section: Introductionmentioning

confidence: 99%

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Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl

1997

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In the (harpooning) reaction Ca( 1 P) + HCl f CaCl(A 2 Π,B 2 Σ + ) + H we study the effect of the long-range interactions between the multipole moments of HCl and the quadrupole moment of the Ca( 1 P) atom, using semiclassical dynamics. The relative translational motion of the reagents is described by classical trajectories, while the rotation of HCl and the evolution of the Ca( 1 P) state are treated quantum mechanically. We pay special attention to the influence of the alignment of the Ca( 1 P) state, investigated experimentally by Rettner and Zare [J. Chem. Phys. 1982, 77, 2416. We find orbital following when this excited state is polarized parallel (Σ) to the initial velocity vector, and we obtain adiabatic and nonadiabatic transitions into the Σ substate when the Ca( 1 P) atom is initially polarized perpendicular (Π) to the beam. Simultaneously, there is a strong tendency of HCl to become orientationally localized, with H toward Ca. It is the anisotropy of the adiabatic potential energy surfaces and the polarization of the corresponding adiabatic states which relate these two phenomena. The initial polarization of the Ca( 1 P) atom is clearly reflected in the orientational distribution of the HCl molecule when it reaches the harpooning radius. From a simple model for the chemical reaction we infer that these long-range effects have an important influence on the A 2 Π/B 2 Σ + branching ratio of the CaCl product, but we cannot quantitatively compute the (experimentally observed) effect of the Ca( 1 P) alignment on this branching ratio.

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Section: Resultssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl

1997

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“…2 If the molecule possesses a dipole moment, then electric fields can be used to effect orientation and alignment. [19][20][21][22][23][24][25][26] Studies by the research groups of Brooks, Bernstein, Loesch, and others have yielded special insight into the steric requirements of reaction. Polarized pumping techniques can also be used to cause reagent alignment.…”

Section: Introductionmentioning

confidence: 99%

Reaction of Cl with vibrationally excited CH4 and CHD3: State-to-state differential cross sections and steric effects for the HCl product

Simpson

Rakitzis

Kandel

et al. 1995

The Journal of Chemical Physics

234

198

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Thermal and vibrationalstate selected rates of the CH4+Cl↔HCl+CH3 reaction J. Chem. Phys. 103, 9642 (1995); 10.1063/1.470731Core extraction for measuring statetostate differential cross sections of bimolecular reactionsThe mechanism for the reaction of atomic chlorine with vibrationally excited methane is investigated by measurement of correlated state and scattering distributions using the method of core extraction ͑see preceding paper͒. Laser photolysis of molecular chlorine creates monoenergetic chlorine atoms ͑Ͼ98% Cl 2 P 3/2 ͒ that react with vibrationally excited methane molecules prepared by linearly polarized infrared laser excitation. The resulting HCl product population distributions are determined by ͑2ϩ1͒ resonance-enhanced multiphoton ionization ͑REMPI͒, and the differential cross section for each product rovibrational state is measured by core extraction. Approximately 30% of the product is formed in HCl(ϭ1,J) with a cold rotational distribution; the remaining population is formed in HCl(ϭ0,J) and is more rotationally excited. We observe a rich variation of the scattered flux that is dependent on the internal-energy state of the product. The HCl͑ϭ1͒ product is sharply forward scattered for low J and becomes nearly equally forward-backward scattered for high J; the HCl(ϭ0,J) product is back and side scattered. The reactions of Cl with C-H stretch-excited methane ͑CH 4 ͒ and C-H stretch-excited CHD 3 are found to have similar angular and internal-state distributions. Observation of the spatial anisotropy of the HCl͑ϭ0, Jϭ3͒ product shows that significant vibrational excitation of the methyl fragment does not occur. The measured spatial anisotropy is most consistent with a model in which backscattered HCl͑ϭ0, Jϭ3͒ is formed in coincidence with slight methyl vibrational excitation and the forward-scattered HCl͑ϭ0, Jϭ3͒ is formed in coincidence with no methyl excitation. The approach of the attacking chlorine atom with respect to the C-H stretch direction can be varied by rotating the plane of polarization of the infrared excitation. A marked steric effect is observed in which Cl atoms approaching perpendicular to the C-H stretch preferentially yield forward-scattered HCl͑ϭ1͒ product. On the other hand, the reaction is weakly dependent on the rotational quantum state of CH 4 ( 3 ϭ1,J), and on the rotational polarization. The data are consistent with a model that has a widely open ''cone of acceptance'' in which the impact parameter controls the internal-state and scattering distributions of the HCl product.

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“…A prerequisite for an experimental investigation of geometric requirements for a successful encounter is control of the directional distribution of the molecular axes prior to collision of the molecules. There are now various experimental techniques available to create anisotropic axis distributions: the electrostatic hexapole method, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] the brute force method, [20][21][22] the optical pumping method, [23][24][25] and the collisional alignment method. 26,27 Since the first conference on chemical stereodynamics was held in Jerusalem in 1986, numerous excellent review articles 28,29 and special journal issues [30][31][32][33][34] on the subject have appeared over the years.…”

Section: Introductionmentioning

confidence: 99%

Stereo correlated dynamics in the energy transfer process of aligned N2 (A 3Σu+) + oriented NO (X 2Π, Ω = 1/2) → NO (A 2Σ+) + N2 (X 1Σg+)

Ohoyama

Maruyama

2012

The Journal of Chemical Physics

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Steric effect for the NO (A (2)Σ(+)) formation in the aligned N(2) (A (3)Σ(u)(+)) + oriented NO (X (2)Π, Ω = 1∕2) reaction has been observed as a function of the mutual orientational configurations between the two molecular reactants in the collision frame. Multidimensional molecular steric opacity function has been determined. A significant NO (X (2)Π) alignment dependence is recognized in contrast with little dependence on NO (X (2)Π) orientation. The NO alignment selectivity turns out to depend on the N(2) (A (3)Σ(u)(+)) alignment: The axial configuration of NO (X (2)Π) is favorable for the axial and sideways configurations of N(2) (A (3)Σ(u)(+)), while the sideways configuration of NO (X (2)Π) is favorable for the oblique configuration of N(2) (A (3)Σ(u)(+)) at an orientation angle of θ(v(R)) ∼ 45°. with respect to the relative velocity (v(R)).

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Reactive asymmetry of methyl iodide. The crossed-beam reaction of oriented methyl iodide with rubidium

Cited by 82 publications

References 0 publications

Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl

Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl

Reaction of Cl with vibrationally excited CH4 and CHD3: State-to-state differential cross sections and steric effects for the HCl product

Stereo correlated dynamics in the energy transfer process of aligned N2 (A 3Σu+) + oriented NO (X 2Π, Ω = 1/2) → NO (A 2Σ+) + N2 (X 1Σg+)

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Reactive asymmetry of methyl iodide. The crossed-beam reaction of oriented methyl iodide with rubidium

Cited by 82 publications

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Entrance Channel Effects in the Reaction of Aligned Ca(1P) with HCl

Entrance Channel Effects in the Reaction of Aligned Ca(1P) with HCl

Reaction of Cl with vibrationally excited CH4 and CHD3: State-to-state differential cross sections and steric effects for the HCl product

Stereo correlated dynamics in the energy transfer process of aligned N2 (A 3Σu+) + oriented NO (X 2Π, Ω = 1/2) → NO (A 2Σ+) + N2 (X 1Σg+)

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Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl

Entrance Channel Effects in the Reaction of Aligned Ca(¹P) with HCl