(a) New laboratory molecular band, superposed on the diffuse interstellar band λ4428 observed toward an O3 If star in the Cyg OB2 association at 1700 pc. (b) The same laboratory band plotted on an expanded wavelength scale, displaying (from right to left) apparent P‐, Q‐, and R‐branches. Features marked by an asterisk denote unassigned lines of light hydrides.