Measurements of the inversion-rotation spectra of the deutero-ammonias have been made in the 7, 000 Mc/sec to 80, 000 Mc/sec region. Thirty-five lines of NH2D and NHD 2 have been measured and identified by means of the Stark effect. As expected, our results show that for these molecules only simultaneous rotational and inversion transitions can be observed. Thus, corresponding to each J-J ,transition two absorption T T lines can be observed, separated by either twice the rotational energy separation or twice the inversion splitting of the levels involved. From our observations the inversion splittings of the partially deuterated molecules can be calculated and are found to be in good agreement with the Dennison and Uhlenbeck inversion doubling theory. Thus the inversion splittings for the ammonia molecules are approximately as follows: 24, 000 Mc/sec for NH 3 ; 12, 000 Mc/sec for NH2D; 5, 000 Mc/sec for NHD 2 ; 2, 000 Mc/sec for ND 3. Our results are also in agreement with the structural parameters of ammonia as given by Herzberg. The sign of the nuclear quadrupole coupling constant was also measured and found to be negative, as expected. The centrifugal distortion for both rotation and inversion states has been experimentally determined.
Long-term performance data has been taken of the NR-6 Johns Hopkins-built hydrogen maser. Data on frequency stability relative to the ensemble of worldwide atomic standards whose data are reported by The Bureau of International de I'Heure (BIH) [1] spans two years. As a clock, this instrument has performed as well as the best standards of Germany and Canada who also report performance through the BIH.
Silver Spring, Maryland summary C ' r y s t a l o s c i l l a t o r s u s e d i n o r b i t i n g satellites to provide a working time scale are s u b j e c t t o drifts i n frequency that cannot be predicted more thsrl a few days a t a time. A frequency synthesizer has been developed that w i l l translate t h e i n p u t f r e q u e n c y t o the output frequency according t o precise mathematical formulation. This device provides the means t o conv e r t t h e s a t e l l i t e c r y s t a l o s c i l l a t o r t o a prescribed frequency that w i l l make t h e s a t e l l i t e c l o c k agree i n r a t e t o c l o c k s on t h e ground. A frequency tuning span of 65 parts per m i l l i o n i s covered i n 38 m i l l i o n d i s c r e t e s t e p s . The movemen't a c r o s s t h i s t u n i n g range i n the s a t e l l i t e is c o n t r o l l a b l e from t h e ground e i t h e r t o s p e c i f i c s t e p s o r t o a rate of progression through the steps. Short term i n s t a b i l i t i e s a t t r i b u t e d t o t h e s y n t h e s i z e r have a one sigma deviat i o n o f 1 p a r t i n IOU averaged over 1 second. Technical Description Block Diwram The b a s i c approach t o t h e s y n t h e s i z e r is shown i n t h e s i m p l i f i e d b l o c k d i a g r a m o f F i g u r e 1. The divide by A is a counter that overflows and resets when it reaches a number s t o r e d i n a r e g i s t e r . The a c t i o n o f overflowing generates a d i g i t a l signal whose fundamental frequency is fo/A. T h i s s i g n a l is combined i n a d i g i t a l v o l t a g e c o n t r o l l e d o s c i l l a t o r ( s i n g l e s i d e band mixer) t o generate a d i g i t a l wave form whose sum frequency is:This waveform is divided by B as above and i n j e c t e d i n t o a v e r y c a r e f u l l y b a l a n c e d a n a l o g s i n g l e s i d e band mixer.The output frequency is then:where B i s the course frequency adjustment and A i s the fine frequency adjustment.The r e s o l u t i o n o f t h e device over i t s operating range is shown i n F i g u r e 2. Having i d e n t i f i e d t h e b a s i c s t r u c t u r e , t h e n e x t l e v e l o f d e t a i l is shown i n t h e n e x t b l o c k diagram, Figure 3. Here w e see t h e A and B counters and the two s i n g l e s i d e band mixers. These counters are cont r o l l e d b y t h e c o n t e n t s o f A and B h o l d i n g r e s i s t o r s . By ground command, Command Data Words are i n j e c t e d i n t o t h e Command Data Word holding register. This word c o n t a i n s t h e d a t a f o r a h o l d i n g r e g i s t e r and t h e i d e n t i f i e r as t o where it belongs; A o r B. There is another means provided for control, through the onboard computer interface. Software programs and d a t a i n j e c t e d from t h e ground, permits t n e computer t o r a i s e o r l o w e r t h e v a l u e o f d i v i d e r number A. Provision has been made f o r t h e n m b e r A to operate between two limits 6300 and 13469. liken e i t h e r limit number i...
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