For the transition from n = 2→n = 1, which of the following will produce shortest wavelength ?

1λ=R1n12−1n22Z2 as n1&n2 are constant ∴  λ∝1Z2more the nuclear charge smaller be the λH = Z = 1D = Z = 1   ∴  Li2+have shorter wavelengthHe⊕=Z=2Li2+=Z=3