Ammonia atomic clock
Reloj atómico de amoníaco
- Date
- 1949 · confidence high
- Place
- Washington, D.C., United States
- Credited to
- Harold Lyons (National Bureau of Standards)
- Field
- Knowledge & symbols
What it is
The first atomic clock, which controls a quartz oscillator with a microwave absorption line of the ammonia molecule (23,870 MHz). Its accuracy did not improve on quartz, but it showed that an atomic transition could regulate time.
The clock was shown in January 1949 at the National Bureau of Standards (NBS); it was soon abandoned for caesium clocks, because the broadening of the ammonia lines limited its accuracy.
What it led to
- the NPL caesium clock (1955)
- the idea of using atomic transitions as a time standard
- national laboratory frequency standards