The wave function is expressed as the exponential of a function: Ψ Ψ ( x ) = e Φ Φ ( x ) , where Φ Φ ″ ( x ) + Φ Φ ′ ( x ) 2 = 2 m ℏ ℏ 2 ( V ( x ) − − E ) . Φ Φ ′ ( x ) is then separated into real and imaginary parts: Φ Φ ′ ( x ) = A ( x ) + i B ( x ) , where A (x) and B (x) are real-valued functions.