Multidimensional Molecular Steric Opacity Function for XeCl*(B, C) Formation in the Oriented Xe* (³P₂, M_J = 2) + Oriented CCl₃F Reaction

Abstract

The steric effect for the XeCl*(B, C) formations in the oriented Xe* (³P₂, MJ = 2) + oriented CCl₃F reaction has been observed as a function of the mutual configuration between the molecular orientation and the atomic orbital alignment in the collision frame. Molecular steric opacity functions have been determined as a function of the atomic orbital alignment (M(L)') in the collision frame. The XeCl*(B, C) channels show similar molecular steric opacity functions at M(L)' = 0 but not at |M(L)'| = 1. The large molecular alignment dependence (i.e., the reactivity of the Cl₃ end and the F end is comparable, but a very poor reactivity for the sideway) is recognized for the XeCl*(B, C) channels except for the XeCl*(C) channel at |M(L)'| = 1, which shows an almost isotropic molecular orientation dependence. The M(L)' selectivity is different between the XeCl*(B, C) channels. At the molecular axis direction, the XeCl*(B) channel has little M(L)' selectivity whereas the XeCl*(C) channel is significantly favorable at M(L)' = 0. On the other hand, |M(L)'| = 1 is favorable at the sideway for the XeCl*(B, C) channels.

Multidimensional steric effect for the XeF* (B, C) formation in the oriented Xe* (3P2, MJ= 2) + oriented NF3reaction

“…The experimental setup and the procedures are similar to our previous study. [13][14][15][16][17] The apparatus is composed of two stateselectors. One is a 40-cm long electrostatic hexapole for the oriented molecular beam.…”

“…We have accomplished the doubly orientationcontrol by using both the oriented NF 3 molecular beam and the oriented Xe* ( 3 P 2 , M J = 2) atomic beam whose configurations in the collision frame are independently controlled. [13][14][15][16][17] A NF 3 molecular beam was generated from a pulsed valve with a stagnation pressure of 50 Torr, and then state-selected by the electrostatic hexapole. The velocity distribution of the NF 3 molecular beam was determined as the stream velocity of v s = 400 ms À1 , and the translational temperature of T trans = 200 K by using a conventional time-of-flight measurement.…”

“…A variety of molecular beam experiments has provided direct observation of steric requirements in chemical reactions. So far, the steric effect on the reactive collision has been studied by using the electrostatic hexapole method, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] the brute force method, [18][19][20] and the optical pumping method. [21][22][23] In general, the steric effect in the reaction dynamics should essentially be seen from a multidimensional perspective because the reaction dynamics between two reactants having anisotropic structure should depend on the mutual orientation between two reactants.…”

“…The direct experimental studies on the multidimensional steric effects on reactive collision are extremely limited. [13][14][15][16][17] The formation of electronically excited rare-gas halide RgX * from the reactions of metastable rare-gas Rg* ( 3 P 2 ) with polyatomic halogen containing molecules RX is important as a benchmark system to study the multidimensional steric effects on reactive collisions because Rg* ( 3 P 2 ) has an anisotropic electronic structure, (n À 1)p 5 ns 1 . The non-closed shell of Rg + gives rise to two different excited rare gas halide product states, RgX* (B, O = 1/2) and RgX* (C, O = 3/2), that correlate with Rg + ( 2 P 3/2 ) and X À ( 1 S 0 ).…”

“…Most recently, we have studied the multidimensional steric effects for the excimer (XeX*) formations in the reactions of the oriented Xe* ( 3 P 2 , M J = 2) with the oriented molecules having a molecular geometry like CY 3 X (e.g., CF 3 I, CH 3 I, CF 3 Br) [14][15][16] and CX 3 Y (e.g., CCl 3 F) 17 which commonly have relatively large quenching cross sections (s Q B a few hundred A ˚2). [24][25][26][27][28][29] Although the X(or X 3 )-end is commonly most reactive as expected from the chemical intuition like ''steric hindrance'' due to the non-reactive bulky group CY 3 (or Y), every system exhibits a wide range of molecular orientation (and alignment) dependence affected by the atomic orbital alignment which does not correlate well with the chemical intuition.…”