This morning I posted a question in Physics Stack Exchange which can perhaps be considered both chemistry problem and a physics problem. Since it has not obtained any attention at all, I am wondering: is it ok if I post the exact same question on this site?
Cross-posting is not considered the correct way to go on Stack Exchange. Or anywhere on the internet, to be a little more precise. The idea is that you want all answers to be in a single common spot, so the best answer out of different alternatives can be easily identified by votes.
That is why, posting the same question twice on a single site will result in it being marked as a duplicate. But duplicates cannot be linked across sites.
If you feel that your question could attract more attention on chemistry, then you can either delete the physics question and repost it here (accepted) or flag it for moderator attention to be migrated (preferred to the best of my knowledge).
The upside of moderator-migration is that it at least keeps a link over at physics for a short time period, allowing users over there to follow the question.
Also note that you can add a bounty to attract more information to a question.