Knudsen manometer

A final example of the application of effusive flow is found in the so-called absolute manometer designed by Knudsen for the measurement of very low pressures. If a disk is suspended near a heated surface at a distance which is small compared to the mean free path of gas molecules, then a molecular effusion will take place between the gas molecules in the space between the disk and surface and the rest of the gas (Fig. VII.8). The rate at which molecules enter this space will be proportional to PgTg, where To refers to the temperature of the gas and Po refers to the pressure. The rate at which molecules leave will be proportional to PsTr, where 5T, refers to the mean temperature of the space between disk and surface and... 

Figure 4.4-1 Basic composition of an apparatus for matrix-isolation experiments a) Rotatable cryostat with gas-handling system, b) Sectional view in the level of the matrix support, (1) matrix support, (2) refrigerator, 4-40 K, (3) radiation shield, 77 K, (4) vacuum shroud, (5) infrared window, X KBr, y PE, z quartz glass, (6) spray-on nozzle, (7) synthetic device, e.g., Knudsen cell, (8) turbomolecular pump, p < 10 mbar, (9) to backing pump, (10) transfer line, quartz or stainless steel capillary, (11) needle valve, (12) inert gas inlet, Ne, Ar, N2,..., (13) bulb for gas mixtures, (14) capacity manometer, (15) sample, (16) to high-vacuum system.

Knudsen effusion Knudsen effusion isoteniscope-manometer gas saturation/effusion ... 

The vapour pressures over CuSe03(cr) and Cu0 CuSe03(cr) were measured with a membrane null manometer and with a Knudsen effusion cell with mass spectro-metric detection by Makatun, Rat kovskii, and Pechkovskii [71MAK/RAT]. The dew point method was used by Bakeeva et al. [72BAK/BUK] for the same purpose. 

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