Topographical Features of Potential Energy Surfaces of the B + O₂ Chemical Reaction

Abstract

Reactivities of spin-orbit states in B( 2 P 1/2, 3/2 ) + O 2 (X 3 Σ g -) f BO(X 2 Σ + , A 2 Π) + O( 3 P J ) have been studied by fluorescence imaging techniques. From experimentally measured reactivities of the 2 P 1/2 and 2 P 3/2 spinorbit states of B atoms toward O 2 molecules and model calculations, an avoided intersection of potential energy surfaces in the entrance valley can be deduced. From the A f X chemiluminescent spectra of BO* products under crossed beam conditions, the spatial patterns of BO* chemiluminescences, and fluorescence imagings of ground state BO radicals, it was inferred that both vibrationally excited BO(X 2 Σ + ) and electronically excited BO(A 2 Π) products are formed in the B + O 2 reaction. The reaction channel that leads to the formation of A state BO* correlates solely with B atoms in the 2 P 3/2 spin-orbit state. On the other hand, half of the population of this 2 P 3/2 level can cross efficiently to a ground state reaction channel, in which the formation of X state BO correlates adiabatically with B atoms in the 2 P 1/2 spin-orbit state. The excited state reaction channel exhibits a small potential barrier, while the ground state reaction channel has an attractive potential energy surface so that the energy release is channeled predominantly into the vibrational mode of BO. Consequently, the avoided intersection of potential energy surfaces and a barrierless, attractive lower sheet are the major topographical features of the B + O 2 reaction.

Oxidation of B, BH, BH2, and BmHn Species: Thermochemistry and Kinetics

“…Chen et al, using a fluorescence imaging technique, investigated the relative reactivities of the spin−orbit states in the reaction B( 2 P 1/2 ; 2 P 3/2 ) + O 2 → BO(X 2 Σ + ;A 2 Π) + O( 3 P 1 ). Their kinetic data and model calculations permitted them to detect an avoided intersection in the potential energy surfaces in the reactant valley.…”

Thermochemical Properties and Electronic Structure of Boron Oxides BnOm (n = 5−10, m = 1−2) and Their Anions

“…Most of the theoretical studies have focused on B n O m species with n as large as 5. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Recently, we predicted the enthalpies of formation and determined the electronic structures of a series of small B n O m compounds and their anions with n ) 1-4 and m ) 1-3 using high accuracy computational methods at the coupled-cluster theory CCSD(T) level with the correlation consistent aug-ccpVnZ (n ) D, T, Q, 5) basis sets extrapolated to the complete basis set limits (CBS) with additional corrections. 23 The calculated detachment energies are in good agreement with the available experimental data.…”

“…Wang and co-workers used experimental photoelectron spectroscopy coupled with quantum chemical calculations to probe the electronic structures of small anions including B 3 O 2 − , B 4 O 2 − , B 4 O 3 − , and B 4 O 2 2− and their neutral counterparts. Most of the theoretical studies have focused on B n O m species with n as large as 5. – Recently, we predicted the enthalpies of formation and determined the electronic structures of a series of small B n O m compounds and their anions with n = 1−4 and m = 1−3 using high accuracy computational methods at the coupled-cluster theory CCSD(T) level with the correlation consistent aug-cc-pV n Z ( n = D, T, Q, 5) basis sets extrapolated to the complete basis set limits (CBS) with additional corrections . The calculated detachment energies are in good agreement with the available experimental data.…”

Determination of k‘−J‘ Correlations of Reaction Products by Fluorescence-Imaging Techniques. 1. Linearly Polarized Excitation Scheme

“…Instead of projecting all the 3D information on angular distributions and angular momentum polarizations in a specific quantum state onto the probe laser direction from an expanding Newton sphere of reaction products, one can employ alternatively two-dimensional (2D) ion-imaging techniques , or the slicing technique of fluorescence imaging − in the study of reaction dynamics. In the present report, we propose a one-photon excited fluorescence (1 + 1 LIF) detection scheme to determine k‘ − J‘ correlations of reaction products.…”

“…[20][21][22][23][24][25] Zare and coworkers have demonstrated the power of the REMPI detection scheme in the study of state-to-state differential cross sections [26][27][28][29] and the three-dimensional (3D) velocity distribution of products 30 in photo-initiated bulb reactions. A theoretical framework that deals with the problem of the angular momentum polarization of products in these photo-initiated reactions has been reported by Shafer-Ray et al 31 Instead of projecting all the 3D information on angular distributions and angular momentum polarizations in a specific quantum state onto the probe laser direction from an expanding Newton sphere of reaction products, one can employ alterna-tively two-dimensional (2D) ion-imaging techniques 32,33 or the slicing technique of fluorescence imaging [34][35][36][37][38] in the study of reaction dynamics. In the present report, we propose a onephoton excited fluorescence (1 + 1 LIF) detection scheme to determine k′-J′ correlations of reaction products.…”