Vibrational excitation through tug-of-war inelastic collisions

Stuart J. Greaves, Eckart Wrede, Noah T. Goldberg, Jianyang Zhang, Daniel J. Miller, Richard N. Zare

Research output: Contribution to journalLetter

Abstract

Vibrationally inelastic scattering is a fundamental collision process that converts some of the kinetic energy of the colliding partners into vibrational excitation(1,2). The conventional wisdom is that collisions with high impact parameters ( where the partners only 'graze' each other) are forward scattered and essentially elastic, whereas collisions with low impact parameters transfer a large amount of energy into vibrations and are mainly back scattered(3). Here we report experimental observations of exactly the opposite behaviour for the simplest and most studied of all neutral - neutral collisions: we find that the inelastic scattering process H + D-2 (nu = 0, j = 0, 2) --> H + D-2 (nu' = 3, j' = 0, 2, 4, 6, 8) leads dominantly to forward scattering (nu and j respectively refer to the vibrational and rotational quantum numbers of the D-2 molecule). Quasi- classical trajectory calculations show that the vibrational excitation is caused by extension, not compression, of the D - D bond through interaction with the passing H atom. However, the H - D interaction never becomes strong enough for capture of the H atom before it departs with diminished kinetic energy; that is, the inelastic scattering process is essentially a frustrated reaction in which the collision typically excites the outward- going half of the H - D - D symmetric stretch before the H - D-2 complex dissociates. We suggest that this 'tug of war' between H and D-2 is a new mechanism for vibrational excitation that should play a role in all neutral - neutral collisions where strong attraction can develop between the collision partners.

Original languageEnglish
Pages (from-to)88-91
Number of pages4
JournalNature
Volume454
Issue number7200
DOIs
Publication statusPublished - 3 Jul 2008

Cite this

Greaves, S. J., Wrede, E., Goldberg, N. T., Zhang, J., Miller, D. J., & Zare, R. N. (2008). Vibrational excitation through tug-of-war inelastic collisions. Nature, 454(7200), 88-91. https://doi.org/10.1038/nature07079
Greaves, Stuart J. ; Wrede, Eckart ; Goldberg, Noah T. ; Zhang, Jianyang ; Miller, Daniel J. ; Zare, Richard N. / Vibrational excitation through tug-of-war inelastic collisions. In: Nature. 2008 ; Vol. 454, No. 7200. pp. 88-91.
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Greaves, SJ, Wrede, E, Goldberg, NT, Zhang, J, Miller, DJ & Zare, RN 2008, 'Vibrational excitation through tug-of-war inelastic collisions', Nature, vol. 454, no. 7200, pp. 88-91. https://doi.org/10.1038/nature07079

Vibrational excitation through tug-of-war inelastic collisions. / Greaves, Stuart J.; Wrede, Eckart; Goldberg, Noah T.; Zhang, Jianyang; Miller, Daniel J.; Zare, Richard N.

In: Nature, Vol. 454, No. 7200, 03.07.2008, p. 88-91.

Research output: Contribution to journalLetter

TY - JOUR

T1 - Vibrational excitation through tug-of-war inelastic collisions

AU - Greaves, Stuart J.

AU - Wrede, Eckart

AU - Goldberg, Noah T.

AU - Zhang, Jianyang

AU - Miller, Daniel J.

AU - Zare, Richard N.

PY - 2008/7/3

Y1 - 2008/7/3

N2 - Vibrationally inelastic scattering is a fundamental collision process that converts some of the kinetic energy of the colliding partners into vibrational excitation(1,2). The conventional wisdom is that collisions with high impact parameters ( where the partners only 'graze' each other) are forward scattered and essentially elastic, whereas collisions with low impact parameters transfer a large amount of energy into vibrations and are mainly back scattered(3). Here we report experimental observations of exactly the opposite behaviour for the simplest and most studied of all neutral - neutral collisions: we find that the inelastic scattering process H + D-2 (nu = 0, j = 0, 2) --> H + D-2 (nu' = 3, j' = 0, 2, 4, 6, 8) leads dominantly to forward scattering (nu and j respectively refer to the vibrational and rotational quantum numbers of the D-2 molecule). Quasi- classical trajectory calculations show that the vibrational excitation is caused by extension, not compression, of the D - D bond through interaction with the passing H atom. However, the H - D interaction never becomes strong enough for capture of the H atom before it departs with diminished kinetic energy; that is, the inelastic scattering process is essentially a frustrated reaction in which the collision typically excites the outward- going half of the H - D - D symmetric stretch before the H - D-2 complex dissociates. We suggest that this 'tug of war' between H and D-2 is a new mechanism for vibrational excitation that should play a role in all neutral - neutral collisions where strong attraction can develop between the collision partners.

AB - Vibrationally inelastic scattering is a fundamental collision process that converts some of the kinetic energy of the colliding partners into vibrational excitation(1,2). The conventional wisdom is that collisions with high impact parameters ( where the partners only 'graze' each other) are forward scattered and essentially elastic, whereas collisions with low impact parameters transfer a large amount of energy into vibrations and are mainly back scattered(3). Here we report experimental observations of exactly the opposite behaviour for the simplest and most studied of all neutral - neutral collisions: we find that the inelastic scattering process H + D-2 (nu = 0, j = 0, 2) --> H + D-2 (nu' = 3, j' = 0, 2, 4, 6, 8) leads dominantly to forward scattering (nu and j respectively refer to the vibrational and rotational quantum numbers of the D-2 molecule). Quasi- classical trajectory calculations show that the vibrational excitation is caused by extension, not compression, of the D - D bond through interaction with the passing H atom. However, the H - D interaction never becomes strong enough for capture of the H atom before it departs with diminished kinetic energy; that is, the inelastic scattering process is essentially a frustrated reaction in which the collision typically excites the outward- going half of the H - D - D symmetric stretch before the H - D-2 complex dissociates. We suggest that this 'tug of war' between H and D-2 is a new mechanism for vibrational excitation that should play a role in all neutral - neutral collisions where strong attraction can develop between the collision partners.

U2 - 10.1038/nature07079

DO - 10.1038/nature07079

M3 - Letter

C2 - 18596807

VL - 454

SP - 88

EP - 91

JO - Nature

JF - Nature

SN - 0028-0836

IS - 7200

ER -

Greaves SJ, Wrede E, Goldberg NT, Zhang J, Miller DJ, Zare RN. Vibrational excitation through tug-of-war inelastic collisions. Nature. 2008 Jul 3;454(7200):88-91. https://doi.org/10.1038/nature07079