[time-nuts] Atomic clocks - Why alkali metals?

[Magnus Danielson]

On 10/29/2011 09:55 PM, J. Forster wrote:
>> Ammonia was the first clock wasn't it?
>
> I think it was an amplifier, not an oscillator. Microwave Amplification by
> Stimulated Emission of Radiation = MASER.

The ammonia clocks was not operating in amplification mode, but in 
absorbtion mode similar to a rubidium gas cell.

The active H maser is the only self-amplifying maser being in wide use, 
all others are passive masers.

Cheers,
Magnus