State-resolved rotational distributions and collision dynamics of CO molecules made in a tunable optical centrifuge
| Autor: | Tara J. Michael, Amy S. Mullin, Hannah M. Ogden |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
education.field_of_study
Angular momentum Materials science 010304 chemical physics Population Relaxation (NMR) General Physics and Astronomy 010402 general chemistry Kinetic energy 01 natural sciences 0104 chemical sciences Rotational energy 0103 physical sciences Physical and Theoretical Chemistry Atomic physics education Anisotropy Spectroscopy Excitation |
| Zdroj: | The Journal of chemical physics. 154(13) |
| ISSN: | 1089-7690 |
| Popis: | State-resolved distributions and collision dynamics of optically centrifuged CO molecules with orientated angular momentum are investigated by probing the CO J = 29–80 rotational levels using high-resolution transient IR absorption spectroscopy. An optical centrifuge with tunable bandwidth is used to control the extent of rotational excitation in the sample. The rotational distributions are inverted with a maximum population in J = 62. Rotational levels with J > 62 have populations that correlate with the intensity profile of the optical trap. The full bandwidth trap excites CO up to the J = 80 level, while J = 67 is the highest level observed in the reduced bandwidth trap. Polarization-sensitive transient spectroscopy shows that the initial orientational anisotropy is r = 0.8 for levels with J ≥ 55, while anisotropy values are near r = 0.4 for levels with J 50 is broadened slightly by collisions, consistent with small |ΔJ| propensity rules for rotational energy transfer. Doppler-broadened line profiles show that the J = 60–80 levels have translational temperatures near Ttrans = 300 K and that these temperatures remain constant for as much as 24 gas kinetic collisions. Doppler linewidths for levels with J < 60 are broadened by non-resonant rotation-to-translation energy transfer. Kinetic analysis of transient signals shows that collisions with thermal bath molecules are the predominant relaxation pathway. |
| Databáze: | OpenAIRE |
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