If you are feeding for flowers you need a potash fertilizer. I haven't heard of using ammonium nitrate, but nitrates in general are used for green crops and foliage.

short answer is no, its not alright for Chrysanthemums - use something more balanced, such as Vitax Q4 in the ground, or Miracle Gro general purpose/Phostrogen Baskets and Container Feed if in pots

True! Straight ammonium nitrate will cause rapid growth, but will eventually exacerbate other nutrient deficiencies, and will delay bloom, at best.