| Autor: |
Deb, Nabanita, Heazlewood, Brianna R., Rennick, Christopher J., Softley, Timothy P. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 4/28/2014, Vol. 140 Issue 16, p164314-1-164314-13, 13p, 1 Color Photograph, 2 Diagrams, 8 Charts, 4 Graphs |
| Abstrakt: |
The laser-induced blackbody-assisted rotational cooling of a linear polyatomic ion, C2H+2 , in its 2Π ground electronic state in the presence of the blackbody radiation field at 300 K and 77 K is investigated theoretically using a rate-equations model. Although pure rotational transitions are forbidden in this non-polar species, the v5 cis-bending mode is infrared active and the (1-0) band of this mode strongly overlaps the 300 K blackbody spectrum. Hence the lifetimes of state-selected rotational levels are found to be short compared to the typical timescale of ion trapping experiments. The v5 (1-0) transition is split by the Renner-Teller coupling of vibrational and electronic angular momentum, and by the spin-orbit coupling, into six principal components and these effects are included in the calculations. In this paper, a rotational-cooling scheme is proposed that involves simultaneous pumping of a set of closely spaced Q-branch transitions on the 2Δ5/2 -2Π3/2 band together with two Q-branch lines in the 2Σ+- 2Π½ band. It is shown that this should lead to >70% of total population in the lowest rotational level at 300 K and over 99% at 77 K. In principle, the multiple Q-branch lines could be pumped with just two broad-band (~Δv = 0.4-3 cm-1) infrared lasers. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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