PTR-MS Neutral Gas Residence Time

The mean residence time of an ion in a drift tube is quite difterent fiom the residence time for a nential gas molecule. For a drift tube with the dimensions considered here, viz., 10 cm long, diameter of 4 cm, and an STPflow rate of 20 cm min the average residence time of the nential gas can be calculated from the volumetric flow rate Fcm s .  

For an internal drift tube volume of 126 cm, the gas should therefore have a residence time in the flow tube of 

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