Lifetimes of Levels in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>12</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>13</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>, and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>13</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>
Аннотация
The Doppler-shift method is used to obtain lifetime limits of $\ensuremath{\tau}<10$ fsec and $\ensuremath{\tau}<26$ fsec for the 3.09- and 3.68-MeV levels of $^{13}\mathrm{C}$, respectively. The radiative width ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$ is remeasured for the 2.37-MeV state of $^{13}\mathrm{N}$ in the reaction $^{12}\mathrm{C}(p, \ensuremath{\gamma})^{13}\mathrm{N}$ and found to be 0.45\ifmmode\pm\else\textpm\fi{}0.05 eV, corresponding to $\ensuremath{\tau}=1.47\ifmmode\pm\else\textpm\fi{}0.15$ fsec. Thus, the disagreement previously reported between the first excited analog levels is not confirmed. A total width $\ensuremath{\Gamma}=34\ifmmode\pm\else\textpm\fi{}1$ keV is found for the level in $^{13}\mathrm{N}$. The Doppler-shift limits are substantiated by observing a lifetime of 55\ifmmode\pm\else\textpm\fi{}7 fsec for the 4.43-MeV level of $^{12}\mathrm{C}$. For the 3.86-MeV level of $^{13}\mathrm{C}$, a lifetime of ${9.0}_{\ensuremath{-}1.5}^{+2.5}$ psec is obtained.
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