The orbital angular momentum of a particle in quantum mechanics is defined exactly as in classical mechanics: if r is the position operator and p is the momentum operator for the particle, then the operator, L, for its orbital angular momentum about the origin is defined by () https://www.w3.org/1998/Math/MathML"> L   =   r   ×   p https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429499265/ff9ae276-bf0f-4700-9154-eaa3ea82fbc6/content/eq832.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>