Optical preparation of H2 rovibrational levels with almost complete population transfer

Abstract

Using stimulated Raman adiabatic passage (SARP), it is possible, in principle, to transfer all the population in a rovibrational level of an isolated diatomic molecule to an excited rovibrational level. We use an overlapping sequence of pump (532 nm) and dump (683 nm) single-mode laser pulses of unequal fluence to prepare isolated H2 molecules in a molecular beam. In a first series of experiments we were able to transfer more than half the population to an excited rovibrational level [N. Mukherjee, W. R. Dong, J. A. Harrison, and R. N. Zare, J. Chem. Phys. 138(5), 051101-1-051101-4 (2013)]. Since then, we have achieved almost complete transfer (97% ± 7%) of population from the H2 (v = 0, J = 0) ground rovibrational level to the H2 (v = 1, J = 0) excited rovibrational level. An explanation is presented of the SARP process and how these results are obtained.

Coherent superposition of M-states in a single rovibrational level of H2 by Stark-induced adiabatic Raman passage

“…In such cases the M-asymmetry of the prepared state will reduce the REMPI fringe contrast, but will not generate the observed discrepancy [see Eq. (12)]. The sharp fringe contrast suggests that we have achieved fairly pure alignment with nearly equal amplitudes in M = ±2 states, that is, C − /C + ≈ −1 and C 0 ≈ 0 as expected from Eq.…”

“…To prepare hydrogen molecules using these resonant techniques, the requirement of appropriate VUV laser sources and ionization loss poses a practical challenge. To overcome these limitations and to transfer significant population to a rovibrational (v, J, M) eigenstate of the H 2 molecule we use a coherent optical technique based on Stark-induced adiabatic Raman passage (SARP), [10][11][12] which does not require an intermedi-ate resonance. Using SARP, we demonstrated nearly complete population transfer from an initial H 2 (v = 0, J = 0) ground state to a vibrationally excited H 2 (v = 1, J = 0) state within the ground electronic surface.…”

“…Using SARP, we demonstrated nearly complete population transfer from an initial H 2 (v = 0, J = 0) ground state to a vibrationally excited H 2 (v = 1, J = 0) state within the ground electronic surface. 12 This was achieved using offresonant Raman pumping with partially overlapping nanosecond visible (532 nm) pump and Stokes (683 nm) laser pulses. The detailed mechanism of SARP has been described in Refs.…”

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

“…Moreover, efforts are underway, in the group of Zare and coworkers, for selective preparation of H 2 molecules in specific vibrational, rotational, and magnetic projection quantum numbers. [161][162][163] Unlike atom-diatom systems, molecule-molecule collisions allow simultaneous changes in rotational and vibrational quantum numbers of both molecules. Since the H 2 molecule exists in both ortho and para-modifications, ortho-para conversion does not occur in non-reactive H 2 + H 2 collisions.…”

A new perspective: imaging the stereochemistry of molecular collisions

“…been used by Zare and coworkers29 to promote HD to well-defined | jm states. Recently, Mukherjee and Zare have developed the Stark-induced Adiabatic Raman Passage (SARP) method for preparing polarized samples [30][31][32][33]. Recently, Mukherjee and Zare have developed the Stark-induced Adiabatic Raman Passage (SARP) method for preparing polarized samples [30][31][32][33].…”