(157)
where X_i is the mole fraction of a component of the beam, C_pi its heat capacity, V_i its terminal velocity, m_i its mass, and T_bi its temperature in the reference frame of the beam. There are several assumptions which have to be made in order to calculate T_o which are reviewed thoroughly in Ref. 29, one of them being high stagnation pressure in the nozzle.
A quick estimate of the temperature T_o can be made by looking at the flux change when the temperatures at the nozzle orifice is varied. The flux emanating from the orifice at constant stagnation pressure depends on the gas temperature in the following way:
(158) 
where the particle density, n(T), varies as 1/T and the velocity of the particles emanating from the nozzle, V(T), goes as the square root of T (see equation (104)). We can therefore estimate T_o by measuring the flux (or partial pressure) with the nozzle heating on and off assuming T_RT=300 K:
(159) 
Also, the gas temperature should be proportional to the square of the observed stagnation pressure (Ref. 65).
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