Which spelling -if any- of ar-Rahmaan is more correct "الرحمن" or "الرحمان"?
The noun ar-Rahmaan and its adjective rahmaan are pronounced with a prolongation of the letter alif between the last two letters meem and noon, nevertheless it is common that people with the name 'Abdurrahmaan ('Abdu ar-Rahmaan) write their names as follows -without an alif in the middle-:
As said earlier this seems to be in contradiction to the pronunciation which sounds more like:
In the qur'an (more exactly in the moshaf) the word ar-Rahman appears with a pendent letter alif which indicates that either the word has two spellings (this would rather be a matter of the science of qira'at, but there's no difference in this context as far as I know) or that the spelling as written in the original text was not in correspondence to the standard language and therefore the letter alif is missing:
I'd like to ask whether both spellings are correct (even if my personal choice would be the later) or if there's a more explicit explanation for the correctness of both or any of them?