Transient Absorption Spectroscopy |
PUMP - PROBE SCHEME |
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Shown here is a diagram describing a typical 2 color experiment. We use the first pulse at the frequency corresponding to the v=0 – v=1 vibrational transition of interest, which in our case is ~3320cm-1. The second pulse is used as a probe and monitors the v=1 – v=2 vibrational transition, which in this case is anharmonically shifted by ~100cm-1 and occurs at ~3220cm-1. The major benefit of doing this 2 color experiment, as opposed to the 1 color experiment, where the 0-1 transition would be both pumped and probed, is that in this scheme, we’re able to uniquely probe the population of the v=1 excited state. Therefore, the population decay that we get, which is described by the equation below, is the pure population decay out of the excited state, free from additional elements that would be in the 1 color experiment, such as stimulated emission. |
