Step 1: Understand the relationship between decay constants.
The decay constant of a substance determines how quickly it decays. For radium bromide, the decay constant is the same as that of radium, since the chemical bonding does not alter the nuclear properties of radium.
Step 2: Decay constant of radium bromide.
Since the decay constant is a characteristic of the isotope and does not depend on the chemical form, the decay constant of radium bromide remains \( \lambda \).