Hydrogen line
https://en.wikipedia.org/wiki/Hydrogen_line
21.106114054160(30) cm in free space. ...
1 420 405 751.768(2) Hz
=>
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50 * 0,2110611405416030 = 10,5530570
78 * 0,2110611405416030 = 16,4627690
115 * 0,2110611405416030 = 24,2720312
193 * 0,2110611405416030 = 40,7348001