Abstract
Transitions from selected nd Rydberg states of H2 to n'p/f Rydberg series converging on the lowest two (N(+) = 0 and 2) rotational levels of the X(+) (2)Σg (+) (v(+) = 0) ground state of para-H2 (+) have been measured in the range 1-7.4 THz using a laser-based, pulsed, narrow-band source of submillimeter-wave radiation. The analysis of the spectra by multichannel quantum-defect theory (MQDT) has allowed a complete interpretation of the fine structures of the Rydberg series and their dependence on the principal quantum number. The extrapolation of the series to their limits with MQDT has enabled the determination of the first rotational interval of para-H2 (+), which is 174.236 71(7) cm(-1) (5 223 485.1(2.3) MHz).
Highlights
Consisting of two protons and one electron, H+2 is the simplest stable molecule
Transitions from selected nd Rydberg states of H2 to n′p/f Rydberg series converging on the lowest two (N+ = 0 and 2) rotational levels of the X+ 2Σg+ (v+ = 0) ground state of para-H+2 have been measured in the range 1-7.4 THz using a laser-based, pulsed, narrow-band source of submillimeter-wave radiation
The relative positions of all Rydberg levels connected by the transitions were used to extrapolate the series to N+ = 0 and 2 series limits using multichannel quantum-defect theory (MQDT), and the set of energy- and internuclear-distance-dependent quantum-defect functions reported in Ref. 22, which were shown in previous work to enable an accuracy in the extrapolation of better than 500 kHz
Summary
Consisting of two protons and one electron, H+2 is the simplest stable molecule. It has two nuclear-spin isomers, para-H+2 and ortho-H+2, with singlet and triplet nuclearspin functions, respectively. N+ = 2 rotational levels of the X+ 2Σg+ (v+ = 4–8) states othfepNar+a-=H+21 and the different hyperfine components rotational levels of the v+ = 4–8 states of of ortho-H+2 These studies provided the fine and hyperfine structure intervals but not the relative positions of the rovibrational levels. Rydberg transitions involving a change in the ion-core rotational quantum number are extremely weak. To overcome this problem, we have recorded spectra from two different initial. The relative positions of all Rydberg levels connected by the transitions were used to extrapolate the series to N+ = 0 and 2 series limits using multichannel quantum-defect theory (MQDT), and the set of energy- and internuclear-distance-dependent quantum-defect functions reported in Ref. 22, which were shown in previous work to enable an accuracy in the extrapolation of better than 500 kHz..
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