Vapour-pressure deficit temperature, the relative humidity and, if possible, the canopy air temperature. We must then compute the saturation pressure. Saturation pressure can be looked up in a psychrometric chart or derived from the Arrhenius equation, a way to compute it directly from temperature is where: To convert between Rankine and degrees Fahrenheit: formula_10 We compute this pressure for both the ambient and canopy temperatures. We then can compute the actual partial pressure of the water vapour in the air by multiplying by the relative humidity [%]: and finally VPD using formula_12 or formula_13 when the canopy temperature is known. Vapour-pressure deficit
Vapour phase decomposition plasma mass spectrometry). This technique, VPD ICP-MS provides accurate measurement of up to 60 elements and detection limits of in the range of 1E6-E10 atoms/sq.cm on the silicon wafer. One related technique is VPD-DC (vapour phase decomposition-droplet collection), where the wafer is scanned with a droplet that collects the metal ions that were dissolved in the decomposition step. This procedure affords better limits of detection when applying AAS in order to detect metal impurities of very small concentrations on wafer surfaces. Vapour phase decomposition Vapour phase decomposition (VPD) is a method used in the semiconductor industry to improve the sensitivity