Direct measurement of spontaneous predissociation using coaxial laser–molecular beams

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Abstract
Radiationless transitions of isolated molecules have been observed using a laser–molecular beam technique. Transitions of the laser excited beam molecules leading to predissociation and other unimolecular processes are detected as a modulation of the molecular beam. Within the 0.05 Å Doppler width of the 5145 Å line of an argon‐ion laser, spontaneous predissociation of the B 3Π+0u state of bromine has been directly observed at wavelengths which produce selective excitation of the individual Br2 isotopic species. The peaks in the modulated mass signal amplitude corresponding to the predissociation process have a width of approximately 500 MHz. Our measurements indicate that predissociation is the predominant decay mechanism of the Br2 B 3Π state at 5145 Å.