Preparing powdered sample for TM-XAS
1. Put some sample in a small agate mortar, use pestle to grind the sample into very fine powder.
2. Cut a piece of hard paper or plastic sheet to make a sample frame as shown.
3. Place a piece of thin Kapton (Polyimide) tape on the frame, sticky side up. Kapton tape should be thinner than.
4. Use sample in the mortar, weigh the right amount of the sample that equals the optimal mass, apply the sample over the sticky window area evenly and homogeneously, make sure there is no “pinhole” in the sample area. Cover the sample area with a Kapton tape.
Preparing liquid sample for FL-XAS
1. Use a liquid cell made of superlene.
2. Cover the cell window with a piece of Kapton tape.
3. Slowly fill up the cell with your sample solution (0.3 mL) by inserting a syringe through one hole. Avoid any bubble.
4. Seal both holes with the tape.
5. Wipe off excess solution on the sample cell.
What is optimal mass?
Optimal mass is a mass of powdered sample that, when applying the sample on a certain area, gives sample thickness corresponding to absorption length of 2. Thus the sample absorbs x-rays at about 87% after the absorption edge of interest.
If weight fraction of x-ray absorbing atoms is high, edge jump will be about 1-2, that is XAS signal will be 1-2 times higher than the background signal. Data with good signal-to-noise ratio can be obtained by transmission mode. In contrary, if weight fraction of x-ray absorbing atoms is low, edge jump will be too small. Fluorescent mode should be used instead.