Investigating Helium Ion's Wavelength Transition

[matpo39]

here is the question I am stuck on:
Radiation from a helium ion He+ is nearly equal to the wavelength to the H_\alpha line (the first line of the Balmer series). (a) Between what states (values of n) does the transition in the helium ion occur? (b) is the wavelenght greater or smaller than that of the H_\alpha line?

my first attempt to solve this was to use the eqation

\frac{1}{\lambda}=R(\frac{1}{n_f^2}-\frac{1}{n_i^2})

and i would set \lambda = 6562.8 \AAthe wave length of H_\alpha but i still can't solve for because both of the states are unknown. anyone have any suggestions on this?

thanks

 

[quantumdude]

You know that n_f and n_i both have to be natural numbers (1,2,3,...). You can start by trying combinations.