Transitions from the 4T2 State in Pink Ruby

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Abstract
In this investigation it was determined by direct measurements that the 4T2 lifetime is less than 2 nsec at temperatures between 2° and 300°K. No fluorescent emission from the 4T2 state was observed although extremely high excitation powers and sensitive detecting equipment were used. It was demonstrated that the nonradiative transitions 4T2→2E occur with a frequency which is greater by a factor of at least 3×105 than that of the fluorescent 4T2→4A2 transitions. If the 4T2→4A2 transitions are considered to be purely electronic, it is shown that the lifetime of the 4T2 state must be less than 45 psec. In the more likely event that the transitions are vibrationally assisted it is shown that the lifetime must be less than 10 psec. Luminescence was observed as the result of a two‐photon absorption process.