Benchmarking Theory with an Improved Measurement of the Ionization and Dissociation Energies of H_{2}.

The dissociation energy of H_{2} represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF ^{1}Σ_{g}^{+}(v=0,N=1) state and the 54p1_{1} Rydberg state of H_{2}. When combined with previously determined intervals, this new measurement leads to an improved value of the dissociation energy D_{0}^{N=1} of ortho-H_{2} that has, for the first time, reached a level of uncertainty that is 3 times smaller than the contribution of about 1 MHz resulting from the finite size of the proton.

Heavy Rydberg states: large amplitude vibrations.

Extremely large vibrational amplitude (≈8700 a.u.) heavy Rydberg levels in the HH[combining macron]1Σ+g state, located only 25 cm-1 below the ion-pair dissociation limit, are reported.

The fundamental rotational interval of para-H2 (+) by MQDT-assisted Rydberg spectroscopy of H2.

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.

Determination of the binding energies of the np Rydberg states of H2, HD, and D2 from high-resolution spectroscopic data by multichannel quantum-defect theory.

Multichannel quantum-defect theory (MQDT) is used to calculate the electron binding energies of np Rydberg states of H2, HD, and D2 around n = 60 at an accuracy of better than 0.5 MHz. The theory includes the effects of rovibronic channel interactions and the hyperfine structure, and has been extended to the calculation of the asymmetric hyperfine structure of Rydberg states of a heteronuclear diatomic molecule (HD).

Spectrum of the autoionizing triplet gerade Rydberg states of H2 and its analysis using multichannel quantum-defect theory.

A new spectrum of the autoionizing triplet states of gerade symmetry of H2 has been recorded from the υ″ = 1–4, N″ = 1–3 rovibrational levels of the metastable c 3Π(u)– state in a supersonic beam. The spectrum consists of overlapping ns and nd Rydberg series with n in the range between 4 and 45 converging to the υ+ = 1–4, N+ = 0–5 levels of the X+ 2Σ(g)+ ground state of H2+. Numerous perturbations caused by s–d and rovibrational channel interactions are revealed in the spectrum and were fully assigned by combining double-resonance experiments and ab initio multichannel quantum-defect theory (MQDT).

A quantum defect model for the s, p, d, and f Rydberg series of CaF.

We present an improved quantum defect theory model for the "s," "p," "d," and "f" Rydberg series of CaF. The model, which is the result of an exhaustive fit of high-resolution spectroscopic data, parameterizes the electronic structure of the ten ("s"Σ, "p"Σ, "p"Π, "d"Σ, "d"Π, "d"Δ, "f"Σ, "f"Π, "f"Δ, and "f"Φ) Rydberg series of CaF in terms of a set of twenty μ(ll('))(Λ) quantum defect matrix elements and their dependence on both internuclear separation and on the binding energy of the outer electron. Over 1000 rovibronic Rydberg levels belonging to 131 observed electronic states of CaF with n∗ ≥ 5 are included in the fit.

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

The most precise determination of the ionisation and dissociation energies of molecular hydrogen H2 was carried out recently by measuring three intervals independently: the X --> EF interval, the EF --> n = 54p interval, and the electron binding energy of the n = 54p Rydberg state. The values of the ionisation and dissociation energies obtained for H2, and for HD and D2 in similar measurements, are in agreement with the results of the latest ab initio calculations [Piszczatowski et al., J.

Communication: The ionization and dissociation energies of HD.

The adiabatic ionization energy [in units of hc, E(i)=124 568.485 81(36) cm(-1)] and the dissociation energy [D(0)=36 405.783 66(36) cm(-1)] of HD have been determined using a hybrid experimental-theoretical method.

Determination of the ionization and dissociation energies of the deuterium molecule (D(2)).

The transition wave numbers from selected rovibrational levels of the EF (1)Sigma(g) (+)(v=0) state to selected np Rydberg states of ortho- and para-D(2) located below the adiabatic ionization threshold have been measured at a precision better than 10(-3) cm(-1). Adding these wave numbers to the previously determined transition wave numbers from the X (1)Sigma(g) (+)(v=0, N=0,1) states to the EF (1)Sigma(g) (+)(v=0, N=0,1) states of D(2) and to the binding energies of the Rydberg states calculated by multichannel quantum defect theory, the ionization energies of ortho- and para-D(2) are determined to be 124 745.394 07(58) cm(-1) and 124 715.