The method of s e n s itiz e d flu o re sc e n c e was used to d e t e r mine cro ss s e c tio n s f o r th e v ario u s e x c i ta t io n t r a n s f e r p ro cesses 2 2 occuring in K -Rb vapour m ix tu res and f o r ** ^3 /2 ™i%ing and 2 2 2 ^1^2 ^1/ 2 ' ^3 /2 quenching in rubidium induced in c o l l i s i o n s w ith se v e ra l d iatom ic and polyatom ic m olecules in t h e i r ground s t a t e s .The a l k a l i vapour in th e flu o resce n ce c e l l , which was kept a t low p re s s u re s to avoid s e rio u s e f f e c t s o f r a d ia tio n im prisonm ent, was ir r a d i a te d by one component of th e a p p ro p ria te resonance d o u b le t.The r e s u ltin g flu o re s c e n c e , which c o n s is te d o f the w avelength component p re s e n t in th e e x c itin g li g h t (resonance flu o re sc e n c e ) and th o se components which aro se from th e em ission by atoms c o l l i s i o n a l l y p o pulated ( s e n s itiz e d flu o re s c e n c e ), was reso lv ed and observed a t r ig h t an g les to th e d ir e c tio n o f th e in c id e n t beam.Measurements of s e n s itiz e d -to -r e s o n a n c e flu o re s c e n t in t e n s ity r a t i o s in r e l a t i o n to rubidium vapour p re s s u re y ie ld e d the fo llo w in g cro ss s e c tio n s fo r e x c i ta t io n t r a n s f e r in K -Rb vapour m ix tu re s: ^1 2 ' ( ^^^1 /2 = 40 f , Qgg, (K4^P^yg ^ Rb$^P^yg) = 2 ?Q i^,(K 4^Pi/2 -, Rb$2p^yg) = 2 .7 Qg^,(K4^Pgyg -Rb^^P^y^) = 1,9 qJ_2(k4^Pi/2 -K4^P^yj = 260 f , and Q^'(KA^P^y^ -KA^P^y^) = 175 In m ix tu res o f rubidium w ith m olecular g a s e s , measurements o f the i n t e n s ity r a t i o s in r e l a t i o n to gas p re s s u re s gave the fo llo w in g c ro s s s e c tio n s fo r th e mixing and quenching c o l l i s i o n s .
The method of s e n s itiz e d flu o re sc e n c e was used to d e t e r mine cro ss s e c tio n s f o r th e v ario u s e x c i ta t io n t r a n s f e r p ro cesses 2 2 occuring in K -Rb vapour m ix tu res and f o r ** ^3 /2 ™i%ing and 2 2 2 ^1^2 ^1/ 2 ' ^3 /2 quenching in rubidium induced in c o l l i s i o n s w ith se v e ra l d iatom ic and polyatom ic m olecules in t h e i r ground s t a t e s .The a l k a l i vapour in th e flu o resce n ce c e l l , which was kept a t low p re s s u re s to avoid s e rio u s e f f e c t s o f r a d ia tio n im prisonm ent, was ir r a d i a te d by one component of th e a p p ro p ria te resonance d o u b le t.The r e s u ltin g flu o re s c e n c e , which c o n s is te d o f the w avelength component p re s e n t in th e e x c itin g li g h t (resonance flu o re sc e n c e ) and th o se components which aro se from th e em ission by atoms c o l l i s i o n a l l y p o pulated ( s e n s itiz e d flu o re s c e n c e ), was reso lv ed and observed a t r ig h t an g les to th e d ir e c tio n o f th e in c id e n t beam.Measurements of s e n s itiz e d -to -r e s o n a n c e flu o re s c e n t in t e n s ity r a t i o s in r e l a t i o n to rubidium vapour p re s s u re y ie ld e d the fo llo w in g cro ss s e c tio n s fo r e x c i ta t io n t r a n s f e r in K -Rb vapour m ix tu re s: ^1 2 ' ( ^^^1 /2 = 40 f , Qgg, (K4^P^yg ^ Rb^P^yg) = 2 ?Q i^,(K 4^Pi/2 -, Rb2p^yg) = 2 .7 Qg^,(K4^Pgyg -Rb^^P^y^) = 1,9 qJ_2(k4^Pi/2 -K4^P^yj = 260 f , and Q^'(KA^P^y^ -KA^P^y^) = 175 In m ix tu res o f rubidium w ith m olecular g a s e s , measurements o f the i n t e n s ity r a t i o s in r e l a t i o n to gas p re s s u re s gave the fo llo w in g c ro s s s e c tio n s fo r th e mixing and quenching c o l l i s i o n s .
2 2 2 2 P ^2 ------P3/2 mixin8 and Pj -----* Si / 2 quenchin8 in potassium and cesium vapors, induced by c o llis io n s with N2> H2, HD and D2, were studied using techniques of se n sitiz e d fluorescence.The m ixtures of a lk a li vapors w ith the various gases, in which the a lk a li vapor pressure was kept low to avoid ra d ia tio n trapping, were irr a d ia te d w ith one component of the appropriate resonance doublet.The fluorescence which contained both components of the doublet, was monitored a t rig h t angles to the d ire c tio n of e x c ita tio n .The measurements of the re la tiv e in te n s itie s of the fluorescent components yielded the to ta l in e la s tic 2 2 2 2 2 cross sections for P mixing, Q12( Pl /2 > P3/2 ^' Q21^ *1/2* P3/2 ^' and quenching, Q10^ P1/2 * S1/2^' Q20^ P3/2 * Sl/2^* In the case of potassium the quenching cross sections for N^, H2> HD and D2 were: Q10 = 35, 7, 11, 2 (£)2 and Q2Q = 39, 4, 14, 1 (£ )2, re sp e c tiv e ly .For the cesium resonance s ta te s the corresponding quenching cross sections O o were: Q10 = 62> 7' 4> 8 ^ and ^20 = 10° ' 5> 3> 7 ^ ' r e s Pe c tiv e ly • The potassium -N2, H2, HD and D2 mixing cross sections were found to be: Q12 = " '7> 75' 6' 74,° ' 72*2 and Q21 = 66*°' 53,2> 50,4, 48,7 re sp e c tiv e ly , only s lig h tly larg e r than the corresponding potassium -inert gas cross se ctio n s.The cesium -N2, H2, HD and D2 mixing cross sections were: Q = 4.7, 6.7, 4.8, 4.2 (£)2 and Q21 = 25.2, 43.8, 32.1, 27.8 (£ )2, resp e c tiv e ly , five orders of magnitude larg er than the cesium -inert gas mixing cross sectio n s. iii R ep ro d u ced with p erm ission o f th e copyright ow ner.Further reproduction prohibited w ithout perm ission.The quenching r e s u lts are c o n sisten t w ith the interm ediate complex th eo ries of quenching in which energy matching between the 2 atomic and m olecular s ta te s is of no importance.The P mixing cross sections do, however, exhibit a marked dependence on the ro ta tio n a l s tru c tu re of the c o llid in g m olecules.The r e s u lts are discussed in terms of induced ro ta tio n a l tra n s itio n s on the basis of which the cross sections ^21^ ^or m^x:'-n8 cesi-uni induced by ortho and para hydrogen are c a lcu lated .
Ths p ro p e rtie s o f newly developed potassium and rubidium s p e c tr a l lamps have been s y ste m a tic a lly in v e s tig a te d in r e l a t i o n to t h e i r o p eratin g parameters* A comparison was made w ith two com m e rc ia lly a v a ila b le lamps* manufactured by Osram and Varian Asso c i a te s !w ith re sp e c t to in te g ra te d in te n s ity * peak in te n s ity * h a lf width* and degree of s e lf -r e v e r s a l of th e resonance l i n e s .I t was found th a t the rad io freq u en cy sources* developed in t h i s laboratory* emit potassium and rubidium resonance lin e s o f s ig n if i c a n tl y h ig h e r peak in t e n s i t i e s and sm aller h alf-w id th s th an th o se produced by th e o th e r lamps.The degree o f s e lf -r e v e r s a l in th e resonance lin e s was a ls o found to be very much more advantageous.T ypical h a lf-w id th s of th e resonance lin e s of potassium and rubidium produced by the r a d io f r e quency source were found to be 0 .1 5 cm.~^ and 0 .j57cm.~^ r e s p e c tiv e ly , compared to th e corresponding widths o f 0 .J 4 cm."* and 1 .5 cm.'* 1
Cross sections for $7^{2}D_{\frac{3}{2}}\ensuremath{\leftrightarrow}7^{2}D_{\frac{5}{2}}$ transfer in Rb, induced in collisions with He, Ne, Ar, and with ground-state Rb atoms, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a noble gas, was irradiated in a glass fluorescence cell with pulses of 660-nm radiation from a N2-laser-pumped dye laser, populating one of the 2D states by two-photon absorption. The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated state. Relative intensities of the components yielded the cross sections for 72D mixing: $Q(^{2}D_{\frac{3}{2}}\ensuremath{\rightarrow}^{2}D_{\frac{5}{2}})=8.8,6.5,10.4, \mathrm{and} 30$; $Q(^{2}D_{\frac{3}{2}}\ensuremath{\leftarrow}^{2}D_{\frac{5}{2}})=5.8,4.0,6.9, \mathrm{and} 18$, in units of ${10}^{\ensuremath{-}14}$ cm2 for He, Ne, Ar, and Rb, respectively. Cross sections for the effective quenching of the 2D states were also determined.
The population and deactivation processes of the first excited 2S and 2D levels of alkali atoms have not been the focus of extensive attention to date, since these levels do not have dipole transitions to the 2S ground state, and the only radiative transitions to the 2p resonance level lie in the IR ( 1-3 fLm). We have demonstrated that in the case of potassium it is possible to populate the 32D and 52S levels in socalled optical collisions by laser excitation of the vapor and also by excitation energy transfer (EET) from the laser-excited Kidimers. 1 The lines of the corresponding 4D--->5P (1.529/1.475 f.lm and 6S ---> 5P (1.367/1.324 f.lm) transitions have also been identified in the laser-induced fluorescence of rubidium vapor,2 although the population mechanism of the levels is not examined in the present study. This st~dy will focus on determining the processes that result in the population of the Rb 42D and 62S levels and to determining the rate constants of these1'rocesses. The spectrum of the LGN-402 argon laser-induced fluorescence of Rb vapors was recorded in the IR by cooled Ge photo diodes selected for IR sensitivity and configured along the outlet slit of an MDR-3 monochromator. The synchronous detection method was employed. A FEU-79 photomultiplier was used in the visible range. Details on the experimental setup can be found in Ref. 3. The Rb vapor was excited by various argon laser lines (514.5-476.5 nm), although the 5l4.5-nm line was of primary interest. The C 1 ITu state of the RB2 dimer is not populated by this laser line; its predissociation efficiently populates the 52P resonance levels4 (see Fig. 1). Moreover the 5l4.5-nm laser line is closer in energy to the Rb 5S--->4D quadrupole transition (M= 75 cm-I). In the experiment at an atomic concentration [Rb] _1016 cm-3 the fluorescence lines from the 62S level (2.5 eV) were weaker by a factor of 50 compared to the lines from the 42D level (2.4 eV). A transition to the shorterwavelength laser excitation lines causes a certain increase in the population efficiency of the 4D level, although it also results in a more rapid growth of the population of the 5P resonance level due to the predissociation of Rb2 (C 1IT u ). I. In pure Rb vapors I) the line intensity of the 4D---> 5P transition has a linear relation to the laser excitation power ,(514.5 nm andp 5X 1016 cm-3 can be attributed to the onset of collisional quenching of the RB 4D state ('Trad =90 nsec). 5 So-called opticaJ.collisions lead to the population of the 4D level in these conditions (Aexc = 514.5 nm and no Na impurities)
in g the o n s e t of d is s ip a tio n at th e ro to n c r i t ic a l v e lo c ity in s u p e r flu id h e liu m .T h is is a c la s s ic a l , c o r r e s p o n d e n c e -p r in c ip le -lim it po in t of v iew and is q u ite an alo g o u s to th e c la s s ic a l d e s c r ip tio n that i s w idely a c c e p te d fo r u n d e rs ta n d in g the e m is s io n of photons by an e le c t r i c c h a rg e th a t m o v e s at a c o n s ta n t v e lo c ity g r e a t e r th a n the sp e e d of lig h t in a d ia le c tr ic m e d iu m .A fte r f i r s t d e riv in g a th e o ry f o r th e w ave e x c ita tio n s and b o u n d a ry -v a lu e p ro b le m s of the c o rre s p o n d e n c e p rin c ip le lim it fo r a co n d en se d -b o so n s y s te m , th is p a p e r show s th a t a w ave r a d i a tio n field f o r m s a ro u n d a fo re ig n body m o v in g th ro u g h the s u p e r fluid m e d iu m w hen the fo re ig n body m o v e s f a s t e r th an the m in im u m p h a se v e lo c ity , {w/k )m jn » w ave e x c ita tio n s in the m e d iu m .M o re o v e r, the sp a tia l d e p e n d e n c e of th is w ave fie ld and the lo s s of e n e rg y r a d ia tin g th ro u g h it a r e c a lc u la te d a s fu n ctio n s of the f r a c tio n a l in c r e a s e of the fo re ig n b o d y 's v e lo c ity above the th r e s h o ld v e lo c ity In s p ite of a p p ro x im a tio n s m a d e in th e c a lc u la tio n s , th e r e s u l t s in d ic a te th a t it is im p o s s ib le , e x p e r i m e n ta lly , to f o r c e an io n c o m p lex to m ove th ro u g h the s u p e rflu id c o m ponent o f h e liu m a t a v e lo c ity o b s e r v a b ly g r e a t e r th an th e ro to n c r i t i c a l v e lo c ity .ACKNOWLEDGMENTS I would lik e to thank P r o f e s s o r R. L. M ills fo r h is c o n trib u tio n s to m y g ra d u a te ed u catio n and fo r h is p e rc e p tiv e c o u n s e l w hile th is r e s e a r c h w a s b e in g c o n d u cted , e s p e c ia lly r e g a r d in g th e re s o lu tio n of s e v e r a l m a th e m a tic a l d iffic u ltie s w hen no so lu tio n s s e e m e d to e x is t.T h e N a tio n a l A e ro n a u tic s and Space A d m in is tr a tio n i s th an k ed f o r i t s fin a n c ia l su p p o rt d u rin g the y e a