Doubly-charged <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>T</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>c</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></

One of the celebrated tools in explaining the hydrogen atom is Born-Oppenheimer approximation. The resemblance of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>Q</a:mi><a:mi>Q</a:mi><a:mover accent="true"><a:mi>q</a:mi><a:mo stretchy="false">¯</a:mo></a:mover><a:mover accent="true"><a:mi>q</a:mi><a:mo stretchy="false">¯</a:mo></a:mover></a:math> tetraquarks to hydrogen atom within quantum chromodynamics implies usage of Born-Oppenheimer approximation for these multiquark states. In this work, we use dynamical diquark model to calculate mass spectra and sizes of doubly charmed and charged tetraquark states denoted as <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msubsup><g:mi>T</g:mi><g:mrow><g:mi>c</g:mi><g:mi>c</g:mi></g:mrow><g:mrow><g:mo>+</g:mo><g:mo>+</g:mo></g:mrow></g:msubsup></g:math>. Our results for mass spectra indicate some bound-state candidates with respect to corresponding two-meson thresholds. Calculation of expectation values of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msqrt><i:mrow><i:mo stretchy="false">⟨</i:mo><i:msup><i:mi>r</i:mi><i:mn>2</i:mn></i:msup><i:mo stretchy="false">⟩</i:mo></i:mrow></i:msqrt></i:math> reflects that doubly charmed and charged tetraquark states are compact. Published by the American Physical Society 2024