Efficient calculation of resonance positions and widths using doubled Chebyshev autocorrelation functions

We demonstrate in this work that two recently proposed doubling schemes for computing damped Chebyshev autocorrelation functions provide accurate information about both the positions and widths of resonances. Low-lying resonances of HN2 and DN2 have been studied using the two efficient methods. The numerical effectiveness of the two methods was found to be comparable. In addition, the HN2 and DN2 resonances have been assigned and analyzed in some detail.