That'll give you a totally different drink. Chartreuse and absinthe both have strong but different flavors; not to mention that a bijou has 3/4oz of chartreuse but that much absinthe would totally overpower any other ingredient.

It would be radically different. I love absinthe but there's a special place in my heart for Green Chartreuse.

Damn, now I want a Last Word.

Chartreuse doesn't really have any good substitutes that I can think of, it's got a very distinct flavour that's nothing like absinthe (I like to lovingly describe it as lawn steeped in everclear).

Still make the drink with absinthe and see how it goes though - it'll taste totally different but it might still be good, and the ABV and (lack of) sweetness of chartreuse and absinthe are at least fairly close.

in the best case you'll invent a new drink but I doubt it'll be very good; start with a very small amount instead of using the same proportions as with chartreuse and you may get somewhere interesting, like a gin sazerac kind of drink