We study the photodissociation chemistry of a quantum degenerate gas of bosonic triatomic $\mathrm{ABC}$ molecules, assuming two open rearrangement channels ( $AB+C$ or $A+BC$). The equations of motion are equivalent to those of a parametric multimode laser, resulting in an exponential buildup of macroscopic mode populations. By exponentially amplifying a small differential in the single-particle rate coefficients, Bose stimulation leads to a nearly complete selectivity of the collective $N$-body process, indicating a novel type of ultraselective quantum degenerate chemistry.

• Received 11 December 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.160402