Observation of an Excited <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>B</mml:mi><mml:mi>c</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math> State
Physical review letters