Their third studio album, Phenomenon was UFO's debut with major label Chrysalis Records and their first to be released in the United States. With the arrival of ex-Scorpions lead guitarist Michael Schenker, Phenomenon saw UFO begin to leave their blues-based "space rock" sound behind and transition to a more straightforward hard rock sound.
"With the Scorpions, I had recorded [the title track of]Lonesome Crow, but 'Rock Bottom' was the continuation of that. I needed to have a song in which I could improvise and go on an adventure. The version that we recorded for Phenomenon had begun in rehearsals as a riff, and we kept adding more riffs to it. And then Phil [Mogg, singer] leapt up and said, 'This is how we'll make it into a song'… I still think of 'Rock Bottom' as a work in progress. When I play it live now, I use the most memorable parts of the solo, and keep a space to represent my latest frame of mind." – Michael Schenker