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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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LOCL-:.;c?;f COHTüCL DATA - RiU
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Cornell Univerrity, Ithaca, NY 14850 UNCLASSIFIED
2ft CKJLil^ N/A J f<^r-C^7 TlfLt
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)
N/A
96 OTHER ^t^ORT MOfSj fAn/of.'iÄf/T-LTi5»r» tt-f nr^y ft» «J J; ^^J tin» rspori)
N/A
Approved for public reiacw«; DUthbutioD UnliuBted
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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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
—fc—~—^'- — ^—— . ^-^m^^mmmm
■■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 - ' - -
<W«n*mM9HM*^NP"m *I|I||HI|IIJL WPmi'W » w»
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).
_—.^-—MB« ■
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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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-e—T 7f«»'"-
kp^p = 0.9 x 10 sec Torr
I SU PP (Torr) r
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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.
(8
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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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