Laboratory Studies of Vibrational Excitation in O( aΔ, v) Involving O, N, and CO.

Collisional removal of electronic energy from O in the low-lying aΔ state is typically an extremely slow process for the v = 0 level. In this study, we report results on the deactivation of O( aΔ, v = 1-3) in collisions with O and CO. Ozone photodissociation in the 200-310 nm Hartley band is the source of O( a, v), and resonance-enhanced multiphoton ionization is used to probe the vibrational-level populations.

Differential cross sections for H + D2 → HD(v' = 2, j' = 0,3,6,9) + D at center-of-mass collision energies of 1.25, 1.61, and 1.97 eV.

We have measured differential cross sections (DCSs) for the reaction H + D(2) → HD(v' = 2,j' = 0,3,6,9) + D at center-of-mass collision energies E(coll) of 1.25, 1.61, and 1.

Time-dependent depolarization of aligned D(2) caused by hyperfine coupling.

Molecular deuterium is prepared in the J = 2, M = 0 sublevel of ν = 1 by stimulated Raman pumping of the ν = 0 S(0) line. Following optical excitation, the degree of alignment of the rotational angular momentum J oscillates in time caused by the coupling of J to the total nuclear spin angular momentum I(T). This coupling is of two kinds, the interaction of J with the magnetic moments and the quadrupole fields of the two I = 1 deuterium nuclei.

Search for Br* production in the D+DBr reaction.

Deuterium bromide (DBr) is expanded from a pulsed jet into a vacuum and a synchronized pulsed laser causes photodissociation of some of the DBr molecules to produce primarily (approximately 85%) ground-state bromine atoms ((2)P(3/2)) and fast D atoms. The latter collide with the cold DBr molecules and react to produce molecular deuterium (D(2)) via two possible channels, the adiabatic channel D(2)+Br((2)P(3/2)) and the nonadiabatic channel D(2)+Br*((2)P(1/2)), which are asymptotically separated in energy by the spin-orbit splitting (0.457 eV) of the bromine atom.

Time-dependent depolarization of aligned HD molecules.

An aligned sample of HD(v = 1, J = 2, M(J) = 0) molecules is prepared under collision-free conditions using the S(0) stimulated Raman pumping transition. Subsequent coupling to the spins of the deuteron I(D) and the proton I(H) causes the initial degree of alignment to oscillate and decrease as monitored over the time range from 0-13 mus via the O2 line of the [2 + 1] REMPI E,F(1)Sigma-X(1)Sigma (0,1) band. The time dependence of the rotational alignment is also calculated using both a hierarchical coupling scheme in which the rotational angular momentum J is regarded first to couple to I(D), and then the resultant F(i) to couple to I(H), to form the total angular momentum F and a non-hierarchical coupling scheme in which the HD energy level structure is not assumed to be diagonal in the |I(H)(JI(D))F(i)FM(F)> basis set.

Preparation of oriented and aligned H(2) and HD by stimulated Raman pumping.

Stimulated Raman pumping has been used to prepare oriented and aligned samples of H(2)(nu=1,J=1,2,3) and HD(nu=1,J=2) under collision-free conditions using the (1,0) S(0), S(1), Q(1), Q(2), and O(3) lines. The M-sublevel anisotropies were interrogated by polarized [2+1] resonance-enhanced multiphoton ionization via the (0,1) O(2), O(3), and S(1) lines of the E,F (1)Sigma(g) (+)-X (1)Sigma(g) (+) system. The optical excitation schemes employed in this study generate highly oriented and aligned molecular ensembles.