Investigation of Nonadiabatic Effects for the Vibrational Spectrum of a Triatomic Molecule: The Use of a Single Potential Energy Surface with Distance-Dependent Masses for H₃⁺

Abstract

On the basis of first-principles, the influence of nonadiabatic effects on the vibrational bound states of H has been investigated using distance-dependent reduced masses and only one single potential energy surface. For these new vibrational calculations, potentials based on explicitly correlated wave functions are used where, in addition, adiabatic corrections and relativistic contributions are taken into account. For the first time, several different fully distance-dependent reduced mass surfaces in three dimensions have been incorporated in the vibrational calculations.

Non-adiabatic effects in the H 3 + spectrum

“…It was augmented with relativistic and QED corrections as described by Lodi et al [4]. The results are presented in table 1, where they are contrasted with those obtained for the same surface with the non-adiabatic Moss mass model of Polyansky & Tennyson [30], the effective mass model of Diniz et al [50] and the effective mass of Jaquet & Khoma [26]. The stockholder AIM results are clearly the most accurate.…”

“…Computed band origins and differences exp -calc, in cm −1 . Nuc, nuclear mass; PT, Polyansky-Tennyson mass [30]; Din, Diniz mass [50]; this work, Stockholder AIM mass; JK, Jaquet-Khoma mass [26]. QED shifts were added to the JK values using the nuc data from [4].…”

“…Bunker & Moss [18] extended the formalism to triatomic molecules [23], and it was applied to the water molecule by Schwenke [24]. Khoma & Jaquet [25], starting from the work of Herman & Asgharian [17], derived an effective rovibrational Hamiltonian for H + 3 and computed vibrational [26] and rovibrational [27] states for this molecule. Their results demonstrated, as did the application of the Bunker & Moss [18] theory to the LiH molecule by Tyuterev and coworkers [28], that, despite considerable computational and numerical difficulties, the numerical results were not yet satisfactory.…”

“…Jaquet & Khoma developed a procedure for determining effective masses from first principles [64] following the perturbative approach of Herman & Asgharian [17]. They also derived the kinetic energy operator for a triatomic molecule taking into account coordinate-dependent masses [26] and included the resulting correction terms in their rovibrational computer program [65]. Their H + 3 mass surface contains contributions from as many as 499 excited singlet states.…”

Comparison of spectroscopic strategies to determine molecular geometries and the impact of nuclear versus atomic masses: the example of HCO+ and HOC+

“…Rescaled masses or distance-dependent masses are also encountered in some applications. 6,27,28 Systematic improvements of the computational approaches are possible only in conjunction with the nuclear masses.…”