Project Title:

Laser Diagnostic for Metastable Molecule-Surface Interaction Measurements

02.03-9030
Laser Diagnostic for Metastable Molecule-Surface Interaction Measurements
Physical Sciences Inc.
P.O. Box 3100
Andover
MA
01810
Marinelli
William J.
17565
49,920
JSC

Abstract:

Multiphoton ionization (MPI) and laser-induced fluorescence (LIF) have been proposed
to detect vibrationally excited states of ground and metastable excited electronic
states of N2 and O2.  Such species as 02(a1delta), N2(A3 ), and N2(X,v>>0) may be
produced and further excited in the shock layer of spacecraft undergoing high altitude
reentry.  The quenching of these species on spacecraft surfaces may result in additional
heat load on the vehicle.  Research has demonstrated the ability to detect O2(al
delta) and N2(X,v) using MPI and N2(A3 ) using LIF in a discharge flow reactor lined
with various spacecraft material.  The reactor can be used to conduct screening tests
to obtain 300K surface deactivation coefficients for these molecules.  A molecular
beam/surface scattering experiment has also been designed.  This equipment can use
a discharge-excited supersonic molecular beam of metastable molecules seeded in He
to achieve translational velocities in excess of 4000K for O2 or N2.  The MPI and
LIF techniques can be used to detect molecules scattered off the surfaces and the
laser polarization dependence of the LIF signal can be used to obtain angle integrated
excitation and quenching efficiencies.