Microwave spectrum of ethyl mercaptan

Volume24A, number 9

PHYSICS LETTERS

s i t i v e to the s a t u r a t i o n i n t e n s i t y of the (22) and (11). F o r the m o d e l c o n s i d e r e d above and in a s o u r c e of f i n i t e extent, s t r o n g (22) and (11) l i n e s w i l l be a c c o m p a n i e d by weak (12) and (21) l i n e s . S a t u r a t e d i n t e n s i t i e s depend on the l e v e l o c c u p a tion and l e v e l widths and a change in the m o d e l c ha nges the i n t e n s i t y r a t i o s . If the (12) and (21) l i n e s a r e dominant and weak, the (22) and (11) l i n e s w i l l be o b s c u r e d by background noise. The c o n c l u s i o n s r e a c h e d in this p a p e r r e q u i r e that the m a g n e t i c f i eld o r Z e e m a n splitting in the s o u r c e m u s t be l e s s than the s a t u r a t e d width of the l i n e , i.e. B<10-6 AWS gauss. U n l e s s c o l l i s i o n b r o a d e n i n g i s a p p r e c i a b l e or the m a g n e t i c f i e l d e x p e r i e n c e d by an atom changes d u r i n g the c o l l i sion l i f e t i m e , m a g n e t i c f i e l d s l e s s than 10-10 g a u s s a r e r e q u i r e d . Although the study is m a d e f o r m o n o c h r o m a t i c l i n e s , it m a y be shown that a ll r a d i a t i o n within the s a t u r a t e d line width t e n d s to the s a m e state of c i r c u l a r p o l a r i z a t i o n . A na i ve a r g u m e n t b a s e d on o v e r l a p m a y be used to a r g u e that the e n t i r e D o p p l e r line s a t u r a t e s t o w a r d the s a m e p o l a r i z a t i o n as the band of f r e q u e n c i e s at line c e n t e r , but a suitable p r o o f is not a pp aren t . A n u m b e r of r e c e n t p a p e r s have r e p o r t e d on the a n o m a l o u s c i r c u l a r p o l a r i z a t i o n in c o s m i c OH s o u r c e s and r e f e r e n c e s to this w o r k i s given in r e f s . 1 and 4. R e f e r e n c e s 4 and 5 have sugg e s t e d m e c h a n i s m s f o r o p ti c a l p u m p in g which

MICROWAVE

SPECTRUM

24 April 1967

could give r i s e to m a s e r action. P a l m e r and Z u c k e r m a n [6] have shown that the m a g n e t i c f i e l d s in the H II r e g i o n s do not e x c e e d 3×10-5 g a u s s and a r e m u c h s m a l l e r than the 10 -3 g au ss f o r Z e e m a n p o l a r i z a t i o n of the radiation. H e e r [1] o b s e r v e d that the p r o b l e m was s i m i l a r to opt i c a l m a s e r studies. A n o m a l o u s p o l a r i z a t i o n in the p r e s e n c e of m a s e r action was p r e d i c t e d in the a b s e n c e of m a g n e t i c f i e l d s and the s o u r c e d e t e c t o r p r o v i d e d the uniqe sp ace axis. T h i s p a p e r p r e d i c t s the p o l a r i z a t i o n of four OH l i n es f r o m the s a m e s o u r c e region. If the r e s u l t s r e p o r t e d in this p a p e r a r e a p p r o p r i a t e , then the m a g n e t i c f i el d in the s o u r c e can be studied and the line i n t e n s i t i e s can be used to study v a r i o u s r e g i o n s of the s o u r c e .

~cfc~'C?ICCS 1. C.V. Hecr. Phys. Rev. Letters 17 (1966) 774. 2. C.V. Heer andR.D.Graft. Phys.Rev. 140 (1965) A1088. 3. H.De Lang and G. Bouwhuis, Phys. Letters 20 (1966) 383. D. Polder and W. Van Haeringen. Phys. Letters 19 (1965) 380. 4. M.M. Litvak, A.L. McWorther, M.L. Meeks and H.J. Zeiger, Phys.Rev. Letters 17 (1966) 821. 5. F.Perkins, T.Gold and E.E.Salpeter, Astrophys. J. 145 (1966) 361. 6. P. Palmer and B. Zuckerman. to be published.

OF

ETHYL

MERCAPTAN

L. M. IMANOV, Ch. O. QAJAR and A. A.ABBASOV Institute of Physics of the Acaderny of Sciences of the Azerbaijan SSR, Baku

R e c e i v e d 17 F e b r u a r y 1967

The microwave spectrum of ethyl mercaptan has been studied in the frequency region between 18 and 33GHz. Numerous P-, Q- and R- branche transitions have been identified, and rotational constants and dipole moments have been determined.

A s p a r t of a study in o u r l a b o r a t o r y a l c o h o l s and m e r c a p t a n s , the m i c r o w a v e s p e c t r u m of ethyl m e r c a p t a n have been e x a m i n e d . The s p e c t r u m was i n v e s t i g a t e d in the r e g i o n f r o m 18 to 33 GHz at - 4 5 o c using a conventional Stark m o dulated m i c r o w a v e s p e c t r o m e t e r .

The s t r u c t u r a l p a r a m e t e r s a s s u m e d f o r p r e l i m i n a r y c a l c u l a t i o n s w e r e t h o s e f o r ethanol [1] and m e t h y l m e r c a p t a n [2]: d(C-H) m e t h y l = 1.100/~ d(C-H) e t h y l = l . 0 9 3 A , d ( C - C ) = 1 . 5 2 4 ~ , d(C-S)= = 1.819/~, d(S-H) = 1.335,~, < H C C m e t h y 1 = 109o40',
Volume 24A, number 9

PHYSICS L E T T E R S

Table 1 Rotational tran3itions of CH3CH2SH

Frequency (Mltz) Transition

Observed *

C.dculated

}01-Ii0 202-211 303-312 404-413 505-514 606-615 707-716

23534.8 24 150.5 25095.8 26397.0 28 087.9 30208.7 32802.0

23534.8 24 150.5 25095.9 26397.1 28 087.9 30208.6 32803.6

111-212 101-202 110-211

20130.7 20722.6 21338.7

20130.7 20722.8 21338.5

212-313 202-303 221L322 220-321 211-312

30 188.6 31054.8 31100.8 31148.8 31999.7

30 188.6 31 054.7 31101.7 31148,8 32000.1

515-422 413-322 414-505

22637.7 25238.7 31241.9

22638.0 25241.4 31243.1

24 April 1967


*All f r e q u e n c i e s accurate to ~0.30 MHz Table 2 Rotational constants and the moments of inertia Observed

A (MHz) B (MHz) C (MItz)

Calculated

28 416.5 5 485.6 4881.7 -0.9486818

la(a .u .m .~2) lb(a.u.m .~2) lc(a .u ,m .~2)

17.79005 92.15600 103.55634

la+Ib-Ic(a.u.m .,~2)

6.3897

References 1. L . M . I m a n o v , C h . O . Q a j a r and I . J . I s a e v , in print.

486

Structure I

Structure II

28 873.0 5 474.3 4885.1 -0.950875

28 463.9 5 490.6 4886.2 -0.948723

17.5088 92.3455 103.4850

17.7604 92.0712 103.4612

6.3693

6.3704

2. T.Kojima, J . P h y s . S o c . Japan 15 (1960) 1281. 3. I . N . S c h o o l e r y and A.H.Sharbaugh, Phys. Rev. 82 (1951) 95.