INSTRUMENTATION FOR COLLISIONRL ENERGY TRANSFER STUDIES I/i (U) MISCONSIN UNIV-MADISON DEPT OF CHEMISTRY F F CRIM 27 OCT 87 RFOSR-TR-87-i78"

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1 INSTRUMENTATION FOR COLLISIONRL ENERGY TRANSFER STUDIES I/i (U) MISCONSIN UNIV-MADISON DEPT OF CHEMISTRY F F CRIM llll m 27 OCT 87 RFOSR-TR-87-i78" AFOSR UNCLASSIFIED F/G 26/5 NL

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3 %.7 * 4 PREPORT... P : AD-A )7s, D,.5 7 T,'C,'j I AVAIL, c.- ITV C r REPORT -b' ON, 0 0-8Lep ro\.d for publ I r2 Ieast. A87, 1 1 Di ';: ",- ion L n i miet o.1, 4 F-', PR.,A%,iZATiCN NU%, 3L is.) 5. MONI1, I,,C ORGANIZ;,TQ,.: )EPOG R4.E,%PERSI T :',~ A FOR -7X- 8 7 "1T t,a. -- VE OF 0 EQFO N..G OiGANIZATION. OFF CE SY.8-0 L a. NAE'L 3F VC NITOIAiNiG OR 5AOZ7TIACN 1I(appiicable Universi v or Wiscons in APO5K.' A,,. RDORELS,C St,;re cnd ii! Code, 7b.,.,DU.ES3!Cti, Stear ane LIP Code i Departer e-.. of Chemistry B~ ', Lni Unlersitv Avenue,!discn, 37 C Bolimn AFB, D. C " 8. NAVE C F.NCN%. S tcr3oring fao. OFFICE S', M1ZL Q PFRCCUREMENT INSTRUMENT IDENTIFCATIOr. NUMt8ER ORGANIZATION If appzlcahe AFOSR NC A FOS R c A 0RESS City. Statre aa ZIP Code) 10. SOURCE or FUNoING 4 CS B d 0 PROGRAM PROJECT TASK WORK UNIT ELEMENT NO NO. NO. NO. BoIling AF: '48 SI' T:TILE,fnc, d iecuri- Ciasifcation, nstru entation :or 61102F 2319 A2 ' C Cj11sicnal Fn-rLr- Transfer Studies _ 12. PERSONAL AJTHORS) F. Cri- 13& T PE OF REPORT 13t. TIME CCVEREO 14 DATE OF REPORT 11'r..',Io.. D>, 1S. PAGE COUNT FROM,/" / 5 Oii._ /&J i937'70/", SUPPLEMENTARY NOTATION -CSAT, Z17 CCDES 18. SUBJECT TERMS icontinue on relerse :f ne es.sary and taettify 5y block number) FIELD GROUP SUB. GR. -.!Molecular energy transfer, Vibrational energy transfer<-, % i" 19. ASST RACT.Contirue on reverse if necessary and identify by bloch number) * Two dye laser systems were purchased for use in energy transfer studies and in '-. V unimolecular decomposition experiments. Individual angular momentum states of acetylene in the fourth vibrational state of the CH stretching mode were prepared. It was found that these molecules which contain 10,000 wave numbers of vibrational energy relax at several times the gas kinetic collision rate. There is a striking dependence on the initial rotational state excited implying relaxation of.* only relatively small amounts of rotational energy. 20 0ISTRi8UTION/AVAILA8ILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION %UNCLASSI'F ED'UNLIMITEO SAME AS RPT.C DTIC USERS Unc lassified 22. %AVME 0;F AESPONS,3LE,NOIVIOUAL 22b TELEPHONF NUMBER [22c OFFICE SYMBOL F.,J.,.;odirczvk 0 76Y-4=0 NC DD FORM 1473, 83 APR EDITON OF I AN 73'S O8'cLfzl L IC LI,s I 1 1 Od SECURITY CLASSIFICATION OF THIS PAG,' 1 I-

4 Final Report 1O.6RA1L " Grant No. AFOSR (15 July 1986 to 14 July 1987) This grant is part of the University Research Instrumentation Program (URIP) that allowed us to advance our DoD sponsored research very significantly by purchasing lasers for use in our collisional energy transfer studies and in our unimolecular decomposition experiments. These benefits have come not only from the use of the hardware on our AFOSR sponsored projects but also by reducing competition for equipment by other projects. The net result has been some dramatic new collisional energy transfer results and spectroscopic measurements in our AFOSR sponsored project. In other DoD sponsored research, we have obtained new data in two photodissociation experiments and a new vibrational overtone spectroscopic measurement. The primary goal of our URIP proposal was to advance our studies of collisional energy transfer in highly vibrationally excited polyatomic molecules. We have now succeeded in preparing 0 individual angular momentum states of acetylene (C 2 H 2 ) in the region of the third overtone of the CH stretching transition 3 vch and monitoring the resulting highly vibrationally excited molecule using ultraviolet laser induced fluoresence. The experiments have three primary aspects: they explore the nature of the highly vibrationally excited state produced by vibrational overtone *'excitation, they exploit the two-photon combination of vibrational excitation and laser induced fluoresence to excite directly pi I1 dita, 2. 7~i

5 2 previously unobservable vibrations in the electronically excited molecule, and they follow the collisional relaxation of individual quantum states in highly vibrationally excited molecules. The collisional energy transfer studies have shown that these molecules that contain cm 1 of vibrational energy relax at several times the gas kinetic collision rate. We note a striking dependence in the probe excitation spectra on the initial *rotational state excited and have tentatitively concluded that the relaxation proceeds by extremely rapid vibrational energy transfer with only relatively small amounts of rotational relaxation. We *. have carefully determined the rate of loss of the excited molecules and are now identifying the final states of the relaxation. We expect to sort out the mechanism of the *. collisional energy transfer and extend the work to other vibrational levels and molecules. The other DoD sponsored research that has benefitted from the increased experimental time available because of the URIP P. hardware is a unimolecular decomposition experiment funded by the I Army Research Office. We have now studied the vibrationally mediated photodissociation of HONO 2 and made the first state resolved measurements on its vibrational overtone induced.,1 decomposition. In the vibrationally mediated decomposition * experiments, one photon excites an overtone vibration and another fragments the resulting vibrationally excited molecule by exciting it to a rrpulsive electronic surface. This approach has revealed unique.photodissociation dynamics, as seen in the quantum state distribution of the products. We have also made the first state

6 3 resolved unimolecular decomposition measurements on this molecule by exciting the fourth (5vOH) or fifth (6v OH) OH stretching overtone vibration and probing the individual quantum states of the OH fragment. h,j I' K..,. 0.1g.J,6!

7 V 'p.5- -'I V / ii ~:0 :0-4 'p ji4~? *1' \h'..~.;5a. ~V' ~ 7.