LASER-BASED DIAGNOSTIC FOR N2(X V)

WE PROPOSE TO DEVELOP TWO LASER-BASED TECHNIQUES TO MONITOR POPULATIONS OF HIGHLY VIBRATIONALLY EXCITED GROUND ELECTRONIC STATE N(2)(X,V>>0) IN A CHEMICAL LASER ENVIRONMENT. THE TECHNIQUES ARE NON-INTRUSIVE POINT DIAGNOSTICS WITH POTENTIAL DETECTION SENSITIVITIES AS LOW AS 10(12) MOLECULES CM -3. ONE TECHNIQUE INVOLVES THE USE OF MULTIPHOTON IONIZATION SPECTROSCOPY (MPI) TO IONIZE N2(X,V) WITH FOUR PHOTONS FROM A TUNABLE LADER USING THE A(1)PIG STATE AT THE TWO-PHOTON LEVEL. IONS FORMED IN THE GAS STREAM WILL BE COLLECTED USING BIASED ELECTRODES. THE SECOND TECHNIQUE EMPLOYS AN OPTICAL DOUBLE-RESONANCE METHOD TO EXCITE N(2)(X,V) TO N(2)(B,V) USING THE N(2)(A) STATE AS AN INTERMEDIATE. FLUORESCENCE FROM N(2)(B) WILL BE DETECTED AS A MEASURE OF N(2)(X,V). THE TECHNIQUES WILL BE CALIBRATED USING THE HE-METASTABLE PENNING IONIZATION TECHNIQUE IN CONJUNCTION WITH KINETIC MODELING. POTENTIAL INTERFERENCES FROM OTHER SPECIES POTENTIALLY PRESENT IN AN INTERHALOGEN TRANSFER LASER WILL BE EXPERIMENTALLY EVALUATED. N(2)(X,V) WILL BE PREPARED BY DISCHARGING N(2)/AR MIXTURES IN A DISCHARGE FLOW REACTOR CURRENTLY IN OPERATION AT PSI. A TANDEM UV-VISIBLE ND:YAG PUMPED DYE LASER SYSTEM WILL BE USED AS THE LASER PROBE SOURCE.