1. How to detect change in absorbance (delta A) spectra in transient absorption spectroscopy using CCD, mechanical chopper?
2. How to measure I(unpumped) and I(pumped) both at different frequencies using chopper synchronized with detector?
3. We tried triggering CCD with chopper frequency and external triggering of chopper to fs laser (1K rep rate). But did not get success in detecting absorbance change.
4. How exactly this process of synchronization works?
Use the sync output on the chopper to trigger your CCD. This will all depend on the CCD manufacturer and software e.g. Roper Scientific cameras typically have a TTL sync port that allows you to use it as a trigger for several of the cameras functions though software. More detail about the hardware will be required to give you more detailed information.
For Princeton Instruments CCD (Roper), I used the TTL output from the camera to trigger fast Uniblitz shutter, without any software. Anyway, one should always verify synchronization prior to measurements as it is never perfect. Some parameters to take into account are:
- time resolution of the experiment,
- what is more important: to prevent extra sample irradiation or to capture the event of irradiation beginning.
Mr. Zhu Hai , Mr. Sergei G Kruglik, Mr. Ron Reiserer, thank you for your responses. But we tried triggering CCD with chopper frequency and external triggering of chopper to fs laser (1K rep rate). But did not get success in detecting absorbance change.
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