Towards measuring the ionisation and dissociation energies of molecular hydrogen with sub-MHz accuracy

Abstract

The most precise determination of the ionisation and dissociation energies of molecular hydrogen H 2 was carried out recently by measuring three intervals independently: the X / EF interval, the EF / n ¼ 54p interval, and the electron binding energy of the n ¼ 54p Rydberg state. The values of the ionisation and dissociation energies obtained for H 2 , and for HD and D 2 in similar measurements, are in agreement with the results of the latest ab initio calculations [Piszczatowski et al., J. Chem. Theory Comput., 2009, 5, 3039; Pachucki and Komasa, Phys. Chem. Chem. Phys., 2010, 12, 9188] within the combined uncertainty limit of 30 MHz (0.001 cm À1 ). We report on a new determination of the electron binding energies of H 2 Rydberg states with principal quantum numbers in the range n ¼ 51-64 with a precision of better than 100 kHz using a combination of millimetre-wave spectroscopy and multichannel quantumdefect theory (MQDT). The positions of 33 np (S ¼ 0) Rydberg states of ortho-H 2 relative to the position of the reference 51d (Rydberg state have been determined with a precision and accuracy of 50 kHz. By analysing these positions using MQDT, the electron binding energy of the reference state could be determined to be 42.3009108(14) cm À1 , which represents an improvement by a factor of $7 over the previous value obtained by Osterwalder et al. [J. Chem. Phys., 2004, 121, 11810]. Because the electron binding energy of the high-n Rydberg states will ultimately be the limiting factor in our method of determining the ionisation and dissociation energies of molecular hydrogen, this result opens up the possibility of carrying out a new determination of these quantities. By evaluating several schemes for the new measurement, the precision limit is estimated to be 50-100 kHz, approaching the fundamental limit for theoretical values of $10 kHz imposed by the current uncertainty of the proton-to-electron mass ratio.

Structure and dynamics of H2+ near the dissociation threshold: A combined experimental and computational investigation

“…Overview PFI-ZEKE photoelectron spectra of para and ortho H 2 in the region of the dissociation limit of H + 2 (at 145796.84136(37) cm −1 above the X(v = 0, N = 0) ground state [42,43]) are displayed in the upper and lower panels of Fig. 1 and to the A + (0, 0) and (0,2) states.…”

Bounds on fifth forces from precision measurements on molecules

“…This suggests that future improvements in the accuracy of the D 2 D 0 [54] can lead to tighter constraints, while in the case of HD + hyperfine interaction need to be addressed more accurately to improve its accuracy. In addition, as the wave functions of the neutral hydrogen molecules extend towards shorter range than the ionic species, the bounds for β at shorter λ is tighter for the neutrals, e.g.…”

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

“…The properties of Rydberg states also depend on the orbital and magnetic quantum numbers and m. The selective production of Rydberg states of well-defined quantum numbers enables one to generate atoms or molecules with specific physical properties. This advantage is exploited in an increasing number of scientific applications in several subfields of physics and chemistry, such as quantum optics (see, e.g., [4,5]), quantum-information science (see, e.g., [6,7]), metrology in atoms and molecules (see, e.g., [8][9][10]), high-resolution photoelectron spectroscopy [11], the sensing of electromagnetic fields [12][13][14], and in research on antihydrogen [15][16][17].…”