Hello.

Since you are an atheist now, you are finally free to search the truth without being bound to a dogma you cannot doubt. The downside is that you will be in constant doubt since every new discovery about reality poses new questions and there is no holy scripture where you can get the ultimate answer.

Can an atheist have a spiritual experience?

I remember when I first saw Saturn in good quality (before that I only had a little, blurry image.) I saw the planet and the ring with the Cassini division, I also saw one of the larger moons of Saturn. Seeing Saturn, and other planets, and other objects for real instead on photographs, was a strange experience. I would say, even a kind of spiritual one. Of course my telescope cannot show all the details of a professionally taken image, but I saw the actual object with my own eyes.

I cannot be certain that the scientific facts about celestial objects never need to be corrected, but I can think in any direction without the fear to violate a dogma of a faith. Because an atheist with a scientific attitude always expects that he could be wrong, he also always expects to learn something new.

You mentioned Sam Harris. He really challenges some of my views, but he does so with good arguments. Since you are an atheist now, you also can think about Harris' arguments freely, with no faith dogma you must maintain.