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AD-784 774

STUDY OF MOLECULAR LASERS

George J. Wolga, et al

Cornell University

Prepared for:

Office of Naval Research Advanced Research Projects Agency

July 1974

DISTRIBUTED BY:

urn National Technical Information Service U. S. DEPARTMENT OF COMMERCE 5285 Port Royal Road, Springfield Va. ^2151

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1. ARPA Order

SEMIANNUAL TECHNICAL REPORT

Reporting Period

1 October 1973 ~ 31 March 1974

660

2. Program Code Number

3. Name of Contractor

<. Effective Date of Contract

5. Contract Expiration Date

6. Amount of Contract for Current Period

7. Contract Number

8. Principal Investigator

9. Telephone Number

10. Project Scientists

D DO msuss.

JUL 29 ISM

EEEoing B

11. Title of Work

0183-8-006252

Cornell University

1 October 1968

30 Septomh^r 1974

$170,000

N00014-67-A-0077-0006

Professor G. J. Wolga

(607)25 6-3962

Professor S. H. Rauer (607) 256-4028

Prolessor T. A. Cool (607) 256-4191

Professor R. A. McFarlane (607) 256-4075

RESEARCH ON MOLECULAR IASERS

Sponsored by

ADVANCED RESEARCH PROJECTS AGENCY ARPA Order No. 660

The views and conclusions contained in thirr document arc those of the authors and should not be interpreted as nocossarily roprosenting the official policies, either expressed or implied, of the Advanced Research Prljects Agency or the U. S. Government.

I

NATIONAI FECHNICAI iraoKMAHON SERVICE

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Cornell Univerrity, Ithaca, NY 14850 UNCLASSIFIED

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biUDY OF MOLECULAR LASERS

Semiannual Report - 1974 S AJTHOR(i) fLs-jt n-un*. Itrsznn:». ini.'ia/J

George J. Wolga Simon H. Bauer Ross A. McFarlane T. A. Cool

R.~.PO R7 CATc

July 1974 I 7o TOTAL NO. OF y \ . ,

-iB- B/ 71> NO OK H^r5

IA CONTRACT OR C.^ANT NO.

N00014-67-A-0077-0006 b. P.^OJtC T MO.

IC A V A 1'-AdILITY/LIMITATIO.'. NOTlCti

So O^l CtN A TO«'5 H5;PO?»T NUM=»--Pfi)

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N/A

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G'Jf .^LEMifiTiSy NOTSS

M/A

12 S-'O-.50^INO MILITARY Ac nvirv

Office of Naval Research

1 J AHiTr'At;;

rihis report describes Research oa Molecular Lasers perfbxtr»d at Cornell Uaiversity during the psrlod 1 Cctoher 197"S - 7,0 April 1974, 'Jhe woik perforred was oriented in five areas. These are:

1. Measurerr.eat of the vibraticnal deactivaticn of }iF(v=l), CO2C00ol) and C0O1) by collisions with atons. The atons ernployed were H, F, 0, N. D, Cz.

2. Measurerrent of the rate of vibraticnal deactivation at low temperature of the bending node of CO,(010) by ArgOR.

3. Corrpleticn of a conpletc ccrnputcr model for the a:.7-0, CO chemical laser system.

4. Study of new H atcm sources for HP lasers.

5. Laser dodile resonance studies of vibration to rotation enerr/ trinscer in FL-'.

rVi n n r'o7w iA73 Unclassified

Sccudty Class-.::ca^Ort

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Technical Report, SummaTy

This report describes research performed at Cornell University

aimed at furthering the understanding of energy transfer and deactivation

mechanisms in chemical and molecular lasers as well as the study of new

laser systems and new chemical sources for leiser systems. This research

is motivated by the interest of the sponsor in chemical lasers as efficient

sources of coherent optical emission. Emphasis is placed upon the develop-

ment of new and efficient lasers operating at wavelengths not px-eviously

available, and upon the basic processes that underlie all molecular lasers.

The methodology enployed consists of laboratory experiments, data

analysis including computer modeling, and literature review.

The work reported consists of results in several areas. These

are:

1. Measurement of the vibrational deactivation of UF(v=l), COjiOCPl) and CO(v=l) by collisions with atoms. Ihe atoms employed were II, F, 0, N, D, Cl.

2. Ifeasurement of the rate ot vibrational deactivation at low temperature of the bending mode of CO2(010) by Arg an.

3. Completion of i complete computer model for the CS7-0, CO chemical laser system.

4. Study of new II atom sources for HP lasers.

5. Laser double resonance studies of vibration to rotation energy transfer in IIP.

Wy deactivation rates upon IIP and CCL by atomi has shown that

not ill KtOBS are efficient deactivates but that some are very efficient.

To further our understanding of these phenomena we shall carry out similar

studies on related systems such as UCl, HBr and CO so that systematic

correlations will beccme non apparent. In particular, the role of orbital

■ .

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degeneracy of the atomic colliding partner proposed by Nikitin as a

determining factor for rapid deactivation, will continue to be studied

as it appears to be operative in our studies to date.

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Atom Deactivation of Moleciilar Vibration — Professor G. T. Wolga

A. HF

We have completed our study of the deactivation of Iir(v a l) by

O, F, and H atoms. This work was written up and accepted for

publication in Chem. Phys. Letters. Our rate determinations for

deactivation by D, CJK and Br and related studies on Df (v B l) are in

progress. A preprint of the above-mentioned publication is appended to this

section.

We have completed our experimental wort; o.i the deactivation of

CO2(00ol) by O, H,D, F, and Ca atoms. This work will be written up

for publication in the very near future.

IICI and ,IBr

Our complementary studies on atom deactivation of HC£(v B l) and

HBr(v - 1) by H, D, and halogen atoms will commence upon the final

completion of the HF and G02 studies.

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I

To be publisiied in Cl.-m. r!>ys. Letters

DB/OTYATION OP HF(v»l) Kt 1-, 0, AND 11 ATOMS

6. P. Quislcy «^ G- J- u'ol£a

kiboratory of Plasma Studies

Cornell University

Ithaca, New York 14850

Abstract

The laser induced fluorescence method has been used to measure

the rate of deactivation of HFCv=l) by F, 0, and H atoms at 300 K. 4 -1

The rate for F-atoms was found to be kp.jfp = 0.9 + .2 X 10 sec

lorr"1, for O-atOM ^^ - 1.0 1 .2 X 105 sec"1 torr-1, and for 3

Jl-atoms, an upper limit to the rate was found to be ^j_Hp <0.5 X 10

sec" torr" . The results are explained qualitatively in terms of a

vibronic to translational energy transfer mechanism.

I/II

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1. Introduction

A lasse bod/ of literature exists on cxpenmental studios of

Vlbrational energy transfer processes involvinf; uy^'^^^^y^t

The initial motivation for this vork was its relevance to the HF

diendcal laser. Subsequent discover)' of anomalous effects such as

the unusual temperature dependence for the \Ml,T self-nlaxatiOR

rate and tlie nagnitude of this rate Cthe absolute nvagnitudc as well

as the relative magnitude coirpared to the V-V rate) have also added

to the great interest.

The present study is concerned with the deactivaticn of HF by

reactive atomic species. These rates are of importance because it

is thought that atoms of this kind have a substantial effect on the

rate of decay of vibrationally excited species. The P and II atom

rates are also needed to characterize the HF laser system for the

purpose of optimizing efficiency.

II. Experimental

The vibratioaal relaxation data reported here were obtained in

a fast flow system with the laser induced fluorescence technique4.

Hie laser source WHS a pulsed HF cheaical laser (SR,. H - I6:lj -if

the transverse electrode type. The laser W» operated multiline and

the gas flow, SF^ and H- mixture, and discharge pulse rate were ad-

justed to give optimum HF v = 1 - v - 0 output. The pulse energy

was 1 mJ SSI of which was on the T>-0 transitions (I* P , p.). The ö 7 8 *

total pulse duration (including 5>2, 2>1, and 1*0 tr.msitions) was

less than 1 jisec.

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^^*l^^*m^*m ' "" IIWIM.L II |l ■limi^lll^lNUIJLHRII H« I IJIII^HHII. I, «nmVfHHHppi^^^m

A sclicmatic dia^nua of the experimental a{^>aratus is showa in

figure 1. There uro two distinct parts to this c^eriroent. First,

the effect of the ato;;is on the population of HF(V"1) is determined

by nsasuring tlie change in the decay tine of tho HF laser induced

fluorescence witli and witliout a discharge in the diluent plus parent

jnolecule flow. Second, the atoiii concentration in the fluorescence

cell was rsasured vdth an EPR spectrometer by recreating all flow

and wall conditions in another section of the flow system (upstream)

with an liPR cavity in the sar.e location relative to the discharge

as was the fluorescence cell.

The procedure was to set up a flow of diluent (usually ar^on)

plus parent rcolecule (^ ■ Fo» ^2» ^2^* ^1^s ^"0W ^s linicluely ^e"

tcrmined by the pressures P- and P- (likewise P. and P..) i^hich were

r.easured with a corrosive gas resistant capacitance manometer. A

small amount of IIP was added downstream (less than 1% of the total

flow) through small holes distributed around the circumference of

the Teflon tube. Tue HF is well mixed with the Ar ♦ X^ flow at the

fluorescence cell.

The microwave discharge took place in a quartz tube. All other

tubes were either Teflon or quartz with a Teflon insert to reduce

vail recombination.

The HF fluorescence was monitored with an In Sb PV detector.

A narrow band interference filter passed only the HF T>-0 R-branch

emission. The overall response of the system was less than 0.5 vsec.

'ihe laser power was reduced to avoid overpumping the HF and thus

eliminating the problems of V-V transfer and heating of the gas due

Mi •■■ -., — ■.....- llllltMilMMM^IIII -... .. . . ■J-. --L .. ... ^

■«WW*^ '•- »■■ - — "w«

to V-R,T cnc!i-;y txansfor processes. The resultant loss in signal

to noise was nado up by the Bionation 8100 - Northcxn Scientific 575

sif,n:il averaging system.

A oaiplete block diagram for the KPR spectnxneter is not shown

in the figure, A detailed description of this systcu will be given

elsewhere. This technique for measuring absolute coacentrations of

gas phase radicals is well knoMl and described by V.'cstenberg5.

The gas flow is along the axis of the high Q cylindrical cavity

in a 10 m i.d. quartz tube. The thin-walled Teflon tube insert

substantially reduces or eliminates wall rcco-nbination and hence

nonuniformities in the atom concentration without significantly

affecting the sensitivity of the spectrometer. Taking the sine-

squared dependence of the microwave magnetic field into account, the

3.5 cm long F.PR cavity gives a resolution of about 2 cm over which

the average atom concentration is detenrmed. 'Ihe usual problems

of saturation of the spin system by lügh power microwave fields and '

broadening due to large anplitude magnetic field modulation were

scrupulously avoided.

The following gas samples were used: F2: Air Products technical

grade (purity > 9Sn0; 02: Linde Uli? (purity > 99,99%}; [Ll Mathescn

IHP (purity > 99.999°,;); Ar: I-'atheson Purity (purity > 99.9995'i); He:

Matheson Purity (purity > 99.99991); HF: Hatheson (purity > 99.90j).

Further purification involved passing each gas (except Iff] through

a liquid nitrogen cold trap. The IIP was purified by trap to trap

distillation between 770K aad 1950K.

1

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■■Br"-"»"^"^"« ——————W«I^P« ■ •—"i

III. Results

For P- and o^ in an ar<'pn diluent, the pertinent energy transfer

proccsr.es in the doactivation of HF (v ■ 1) arc: }; 11 HF (v ■ 1) ♦ HF (v - 0) -/ 2IiF (v " 0) (1)

HP (v ■ 1) ♦ X7 (v ■ 0) I2 HF (v ■ 0) ♦ X. (v ■ 0) (2)

m: (v - 1) ♦ Ar I3 HP (v ■ 0) + Ar. (3)

These apply while Hie jaicrowave discharge is off, and the decay time

of the fluorescence is given by:

-J- . }Cii [in.] ♦ k^ [x^] ♦ k^ [Ar]. (4)

'fhis assumes that [IIP (y ^ i)] is nail.

When the microwave disdiarge is turned on, so;?.o of the X? is

dissociated giving an additional channel for doactivation:

HF (v - I) ♦ X * HF (v ■ 0) ♦ X, (5)

In this case, the decay time of the fluorescence is given by:

■i- ■ k11 [HP] ♦ k12 ([X2] - fXI) ♦ ku [Ar] 4 ki4 [xl. (C))

The difference bet^eon (6) and (4) gives:

k14 = Ir- 14 m i) oJ 12 • 2

CO

Tue rates used for k10 were: for 0« • ^ - ^«w» -' ' * "^ 12 k12 ■ 400 sec torr

and for F2 k12 ■ 100 sec torr . 'Ihese turn out to be negligible

correctiens.

.The inportancc of using the EPR spectrometer for measuring.[X]

is that it allows one to detcrmLne the absolute concentration of the

•tonic species in a fast flow system without the need to alter the

flow (as In titration or catalytic probe methods] or even to know

«hat the flow rates are. For F and 0 atoms, the absolute accuracy

of the EPR measurement of concentration is better than 10$.

UM.^^M^MMM - ' - -

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Anotitcr source oC error Is in noasurine the dungo In the total

fluorcsccencc- decay rate. For 0 and P RtOOBi tho change if. slfiniflcont

and hence the error is snail ( 101). A typical mi shevins the change

in decay rate of HP (v ■ 1) in a mixture of Ü, 02, Ar and 111-' as a

function of 0 atom partial pressure {?0) is shewn in figure 2. Similar

results v;erc obtained vith fluorine.

Using equation (7), one can plot (T^ - T^ ) as a function of

atom partial pressure. *lhe result should be a straight line of slope

equal to the atom deactivation rate k-* and intersecting the origin.

Hie results of such a plot for the }: and 0 atom data are shown in

figure 3. The rates determined from these cbta arc:

T-HF ■ 0.9 + 0.2 X 104 sec"1 torr"1

IU-UB ■ !•• ♦ 0.2 X 105 sec"1 torr"1. 0-Hr

For the case of H atoms, the energy trar.sfer is complicated by

the near resonance of the first vibrational levels of 11, and HP. This

gives rise to a double exponential decay . 'Ihe fast decay is due

to V-Y transfer from HP to U2 and Hl: SOlf-TelaXBtion, and tiie slow

process is related to the decay of the H2 - HP vibrational energy

pool through V-R,T transfer from HP(v»l). Ihe ato.TS would be expected

to effect this slow rate by deactivating both II2Cv-l) and HF(v=l).

'Ihe former rate is known to be :

ktuy = i-0 i 0-5 x i^ S(JC"1 torr"1-

However, under no circumstances was there any change observed

due to the presence of II atoms.

S

IIMT ■

II 11 • I immm II I I , vmmm^mmmm^^

Thu only safe tliinj» tliat one can say in this case is that tlw

hyilro-.-n atoos arc not as effective as 11^, in relaxing Hl:(v-l). 'iliis

r9 puts an upper limit on the atom deactivation rate oi :

V < V HI-HP Ti

,. < o.r. x lO5" .sec"3 torr .

IV. Conclusion

These and other prelimnar>' rcsidts of this laboratory

0), M on liFCv--])11; 0, Cl, H on CO2(C01)12) lend support to thu non-

adiabatic theoiy of Nikltin vliidi is based on fi vibronic to tr»9-

lational energy tninsfer r.cchanisn. Briefly, as it applies to our

experiir^nts, ato.ns witl^ electronic orbital angular nomsntun def.eneracy

would be expected to be rore efficient in transferring vibrational

cnerg)' from m:C\^l). During a collisional encounter, the degeneracy

whicli exists at infinite separation is split and electronic transitions

arc possible between these states. V.hen the frequencies of the

electronic transition in the atoiii and the vibrational transition in

HP become equal, there is a large increase in the cross-section for

energy transfer.

This say -. nothing of the possibility for fast, relaxation caused

by atom exchange or abstraction reactions v.hich could predominate

under favorable conditions. This certainly appears to be true in the

case of 0 and H atoms "deactivating" vibrationally excited 1IC1 .

However, it does not appear to be important for the F and H atom

encounters with IlI:(T=30üOK). This Is supported in part by the recent

calculations of O'Meil, et al ' which surest a minimum barrier lieir.ht

for the exchange r<acLi:jn:

V + Hl:(v-0) -y ni(v-O) + F of 18 kcal/molc.

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Previous high tcropcratiiro results for the dcoctivation of

HF(v-l) by F-atons have been reported2»16»17. yh choose to coopare

our results idth those of Blair, et al2. This is show., in the

Landau-Tellor plot of figure 4. The rather si^stantial tciiperature

nnge of 10000K over which there is no rate measurement precludes

the drawing of any but the most speculative conclusions. This figure

does show however that the trend establi hed at high temperatures,

for the decreasing effect of F atoms on HF(v-13 with decreasing

temperature, persists at least to room temperature (300oK). 'Hio

tenperature dependence of the pure liH relaxation rate2 is shown for

comparison.

Clearly, more rate measurements are needed above and below room

temperature before anything definitive can be said about the effects

of long range forces or chemical bonding on the efficiency of re-

active atoms in deactivating IJF(v=l).

Acknowledgements

-ihis work was supported by the Advanced Research Projects Agency

Older ARM Order 660. Ma acknowledge support of the Cornell University

Material- Science Center for the use of central facilities.

Helpful discussions with Professor S. H. Bauer, Professor T. A.

Cool, Dr. M. I. Buchwald and Dr. W. D. Bfeshears are gratefully

appreciated.

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References

1. K. A. l.udit and T. A. Cool, J. Chcm. Pliys. 60, 1026 (1974).

2. I, S. Blair, W. D. Brcslirars, and G. L. Schott, J. Chera. Wiys,

59, 1S82 (1973).

3'. R. M. Osfiood, Jr., P. B. Sackett, A. Javan, J. Oiem. Phys. 60,

1464 (1974).

4. L. 0. Hocker, M. A. Kovacs, C. K. Rhodes, G. W. Flynn, and A. Javaa,

Phys. Rov. Letters 17_, ?.35 (1966).

5. A. A. V.cstenheiT., PROG. IN REACT. KIN., Vol. 7, Part I, 23 (1973).

6. M. M. Green and J. K. Hancock, IEEE JQH, Vol. QE-9, 50 (1973).

7. J. F. Bott and N. Cohen, J. Chen. Phys. 58, 4539 (1973).

8. S. S. Fried, J. Wilson, and R. L. Taylor, IEEE JQH, Vol. QH-9,

59 (1973).

9. J. K. Kanoock and W. H, Green, J. Chen. Phys. 57, 4515 (1972).

10. R. r. HeiuJiex i'.nd J. V. V. Kasper, Gieiii. rhys. I.elleis 15, 179

(1972).

11. G. P. Quisle/ and G. J. Kblga, to be published.

12. M. I. Puchwald and G. J. Volgßt, to be pi^lislied.

13. E. E. Mkitin, Opt. Spectr., 9, 8 (1900).

14. D. Arno]di and .T- Molfrum, Chen. Phys. Letters 24, 234 (1974).

15. S. V. O'Neil, H. F. Scliaefcr III, and C. F. Bonder, Proc. Nat.

Acad. Sei. USA 71, 104 (1974).

16. If. C. Solomon, J, A. Blauer, F. C. Jayc and J. G. Hnat, Int. J.

Chein. Kiltet. 3, 215 (1971).

17. J. F. Bott and N. Cohen,'J. Che.n. Phys. 5^, 5124 (1971).

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Figure (.'njiliuns

Figure 1. A schematic diagnua of the cxpsriraenta] apparatus.

Figure 2. Scoilog ploL of relative intensity as a functim of tiaio

for different disdmrge cemditions in Ar ♦ 0^.

Figure 3. Distribution of data points as calculated fron Cq. (7)

about the measured atom deactivation rales for (a) F on

HF(v-]) and (b) 0 on IIF(v»l).

Figure 4. Landau-Teller jilot oC the temperature dependence of the

F atom deactivation of lil:(v-l).

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P^F-HF THIS WORK

PrF-HF (BLAIR, ET AL.)

1 I

0.08 0.10 0.12 T-'/3(oK)-i/3

0.14

1

0.16

14.

'piWduiMimiiMJ

X-ray diffraction photographs wore taken to determine the correct x and

y axou. A crystal of 1 cm. in length was cut and polished with the normal to

the entrance and exit faces at 15° to the outer axis. This crystal v/as

found to produce second harmonic output when pumped with the TEA laser.

To check on the accuracy of the axis determination a second crystal was

cut oriented with the other choice of quadrants. As expected no S. E.G.

was found for this orientation.

To reduce the 1" beam diameter of the TEA laser to something less than

the 7 mm. transverse dimension of the Te crystal, a folded optical system

was se. up using convex mirrors to converge the beam and provide an

energy density at the Te crystal surface somewhat less than tiie surface

damage threshold. By placing the Te crystal almost in contact with the

fluorescence cell no additional optical elements are rcquJred in the second

harmonic bear,..

The fluorescence cell is made from a stainless steel tee which is a

standard vacuum fitting by incorporating three sapphire windows: two to

pennit the second harmonic beam to traverse the coll and a third for

observing fluorescence at right angles to the beam direction. The cell is

one of a series of elements in a vacuum line through which gas is flowed

first past a microwave discharge cavity and then prior to entering the cell

through a high Q E.P.R. cavity to bo employed for absolute species

concentration determination. Stainless steel and teflon materials have

been used throughout the system for cleanliness and the vacuum integrity is

such eis to permit soalcu-off opeialion over several hours if this is lequ'ied.

Pressure measurements are made by a Pirani gauge, thermocouple and oil

manometer. A two stage Roots blower with a pumping speed of 100 c.f. m.

is used to exhaust the system. This is backed by a 15 c.f. m. Precision

Scientific forepump. The blower is rated at an ultimate pressure of less

than 10 Tonr.

lie.

^—M. MMawaa aa_BalaaaM^_^ — ...... -—

a precision multiplier (Analog Devices Model AD530J) and the output Is

integrated in a low drift integrator (Analog Devices Model 43J). The other

input to the multiplier is derived from the 70 kHz oscillator through a

variable phase shifter. Level set, modulation and correction signals then

drive a high power operational amplifier which provides the Gunn oscillator

current.

The magnc b supplied from a Hewlett Packard 0 - 600 V, 0-20 Amp. power

supply. The basic stability of this supply wuS approdmately 1:3000 and

it was found to be inadequate for +ho E.P.R, measurements intended. A

secondary regulation system referenced to a low temperature coefficient

0.04 ohm resistor which passes the total magnet current was built and is

now operating. This is driven, from a level set and field scan circuit to

provide selected All increments in selectable time i)eriods. E.P.R, spectra

of atomic oxygen have been recorded and more than adequate resolution is

available for the concentration measurements planned. Some difficulty is

being experienced with the microwave discharge causing interference with

the magnet power supply and secondary stabilizer. Inductors are being

installed in all coirection signal lines and it is expected that this problem

wlU be corrected directly.

When the E.P.R« cystem is operational it will be incorporated into the

gas flov\ system described above. Initial measurements of o on CO will

employ NO titration for atom concent ration determination. Our first

efforts to observe CO fluorescence have begun.

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c • Study of Chemical Larjor Systems - - S. A, Bauer

During the first quarter of this year the experimental part of our project

on laser induced fluorescence from the bonding mode of CO was completed.

The results of this study were presented at the April ACS Meeting in

Los Angeles. The 2. 8|x laser emission from HF [Si' + H. I He,

electrically pulsed] is partially absorbed by carbon dioxide. HF linos at

3622.71, 3577.8 and 3644.16 fj.m pump tho (02°!) level, that at 3693.50 u

pumps tho (11 1) level, and both 3593.80 and 3577.80 pump tho (0311) level of CO ,

Line center frequency mismatching is rectified partially by pressure broadening

with argon, or with mixtures which incoroorato other collision partners

of interest. At C02 concentrations above 2^, collisions with the (00o0) state

rapidly degrade tho pumped states to overpopulate the (00o.l) and (0n£0)

states, from which fluorescence is observed at 4.3|x and 15.0m respectively.

The latter showed an early growth, followed by a fluorescence decay such

that the total fluorescence intensity could be represented by a superposition

of two exponentials. Tho longer period was associated with v-T do-

excitation of CO, for which the values:

k(CO Ar) s 41 secTtorr" , and k(CO,-COJ = 227 sec^torr"1

wore deduced. Those check reasonably well with extrapolated shock tube

measurements and ultrasonic data. Tho rate constants for pumping

(On '0) proved to bo about twice tho literature values for tho (0001)

de-excitation: ~ 120 sec" torr" for CO, - Ar and 660 scc^torr"1 for

C02 " C02* As yet the W^rtwwtion for this is not clear. Corresponding

values were also measured for two additional collision partners, CS

and COS .

Tho assembly of data and the preparation of a complete computer

program for the CS2 - 02 - lie chemical laser model system was

comploted. This was also roportod at the Los Angeles mooting. While

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for onset of lasing as a function of upper vibrational state. The effect of

added cold CO was also Investigated, in the third port, relative populations

of excited states, as present at a sequence of delays after pulse initiation,

were obtained from ehemiluminesconce data, in the absence of lasing.

A set of 25 reactions with corresponding rate constants was selected

such that the computed time evolution of the chcmiluminescence intensity

reproduced the observed distribution over the interval 40 - 400 \iS.

Finally, visible and UV spectra emitted during the induction period for

lasing were recorded. A complete report is being prepared.

We also discovcrcd conditions for operating our axially excited

CS -I O + He laser so as to obtain stimulated emission for the (1 > 0) CO

transition. These Studien have been summarized in a brief paper which

will be submitted to Chemical Physics Letters.

A detailed report on the use of H^CO and D^DO polymers as sources

for hydrogen (or deuterium) in III' (or DF) TEA pulsed lasers has been

prepared. On a mole/mole basis formaldehyde, which can be readily

generated from the solid polymer by gentle heating, is approximately 10 time;

more effective for lif laser generation than a comparable quantity of

hydrogen (or de\ 'eüum). This Is a vety practical development which

liberates the user from carrying hydrogen at high pressures in massive

cylinders. Further work with the CW configuration is underway.

Finally, the high powered C02 TEA laser has bee -i completed and is

in process of being checked out. It will be used for the rapid pyrolysis of

boron containing species in mixtures consisting of boron compound with

compatible oxidizers.

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