  We calculate the binding energy, transition energies, oscillator strength,
and absorption coefficient of indirect excitons in transition metal
dichalcogenide (TMDC) double layers separated by an integer number of hexagonal
boron nitride (h-BN) monolayers. The absorption factor, a dimensionless
quantity which gives the fraction of incoming photons absorbed by the indirect
excitons in the double layer, is evaluated. The aforementioned optical
quantities are obtained for transitions from the ground state to the first two
excited states. All quantities are studied as a function of the interlayer
separation, which may be experimentally controlled by varying the number of
h-BN monolayers between the TMDC layers. Calculations are performed by using
the exciton wave function and eigenenergies obtained for the Keldysh potential.
For each material, we choose a combination of the exciton reduced mass and the
dielectric screening length from the existing literature which give the largest
and the smallest indirect exciton binding energy. These combinations of
material parameters provide upper and lower bounds on all quantities presented.
Our findings can be examined experimentally via two-photon spectroscopy.
