In the context of "Brightness in my heart" what is needed (I feel) is more like : i - préposition (place)i - pronoms prépositionnels (ionam, ionat, ann, inti, ionainn, ionaibh, iontu)
Welcome to the forums.
I only speak a little Irish Gaelic (Gaeilge), and no Scottish Gaelic (Gàidhlig) at all, so I cannot be much help to you.
However I do wonder if petit1 is a native Scottish speaker ; since the word ann (adv) means there (in Irish at any rate), unsure where it fits in your sentence.
The English Scottish gaelic dictionaries give "ann".
The Scottish Gaelic equivalents are listed (in that linked on-line dictionary) as follows :In the Irish version of in = i becomes in before vowels, combines with an to form sa before consonants and san before vowels ; combines with na to form 'sna
Source : My trusty Oxford (pocket) Irish dictionary.