User Guide –
Estimating required beamtime
High-Resolution Gas Phase experiments:
In general, at least one week (15-18 shifts, each shift is 8 hours) of beamtime is recommended that for a high-resolution gas phase experiment. This generally gives time enough to run 2-5 different sets of conditions (depending on the requirements).
A more accurate estimate can be generated using the following estimates:
- Scanning time:
The following equation can be used to estimate the time required for each scan (in Seconds).
Where RES is the resolution and VEL is the Velocity in kHz
Typically, a velocity of 80 kHz is used, so for a resolution of 0.00096 cm-1 each scan takes ~6 minutes.
The number of scans required is dependant on a variety of factors, including the region of interest, absorption strength, spectral congestion etc. However, typically 120 scans are the minimum recommended. 240 scans typically are adequate for most spectra.
Generally, background spectra are collected at 16 times the resolution used for the sample spectra. In general, it is recommended that you collect the same number of background scans as you plan to collect for the sample. In general allowing 2-3 hours for each required background is sufficient.
One shift should be allocated for set-up.
- Change of spectral region:
If several spectral regions are required, 2 shifts should be allocated for each change in spectral region.
- Change of temperature:
1 shift should be allocated for any temperature change plus 2 hours for each 10 degrees of temperature change.
The exception being for temperatures below 200 K, where the liquid nitrogen injection system is required, in which case another 5 shifts should be added on top of the above for the set-up and take down of the liquid nitrogen injection system.
- Glow Discharge:
5 shifts should be added for the set-up of the discharge cell.
- Tube Furnace:
5 shifts should be added for the set-up of the Tube Furnace.
Typically, no time is required for cleaning. However, under some circumstances, up to 6 shifts might be required for cleaning out the cell. For example, some samples like ammonia, acids or D2O are difficult to remove from the cell so long periods of evacuation and repeated purges are required to properly clean the cell. If you are unsure about your situation, please contact the beamline staff.
- “Remote” access:
Since beamline staff cannot be at the beamline 24/7 delays can occur, furthermore, delays can occur due to delays in communication between the user and beamline staff. To account for this we suggest that you add 33% to your request for remote access.
It is important to note that the above are just rules of thumb, often careful planning can reduce the required amount of time significantly compared to the above and for some experiments, there may be difficulties that would require more time. It is advised that you contact beamline staff while planning your experiment.
Low Resolution condensed phase experiments:
It is more difficult to estimate the time requirements for Low-Resolution condensed phase experiments, as typically data collection is relatively quick and is not the limiting factor. As a rule of thumb, we recommend that at least 6 shifts be requested, however depending on the number of samples and difficulty of the experiment more are often required. Please consult beamline staff when estimating your requirements.