Experimental Born–Oppenheimer Potential for theX1Σ+Ground State of HeH+: Comparison with theAb InitioPotential

Ab initiocalculation of the 66 low-lying electronic states of HeH+: adiabatic and diabatic representations

“…From an experimental point of view, a numerical procedure particularly successful when data are fragmentary has been employed by Coxon and Hajigeorgiou (1999) to inverse the spectroscopic Bishop and Cheung (1979).…”

Cross Sections and Rate Coefficients for Vibrational Excitation of HeH+ Molecule by Electron Impact

“…Figure 2 shows the potential energy curve V(R) and wave functions for four vibrational levels v = 0, 1, 2, 8. Energy differences for transitions v → v + 1 and rotational constants of the HeH + vibrational levels are listed in Table 1 and compared with previous benchmark calculations [25,26]. Once vibrational energies, wave functions, and geometry-fixed S-matrix are calculated, the scattering matrix describing the transition amplitude S i ,i from one vibrational level v to another v is obtained using the method of vibrational frame transformation [19,27].…”

Non-Born–Oppenheimer calculations of the pure vibrational spectrum of HeH+

“…56 The above form of the reduced mass with the additional adjustable parameter q enables the reproduction of the spectral data of 4 HeH + with the normalized standard deviation of ˆ= 1.2056, whereas without the adjustable parameter ͑q =0͒ the standard deviation of the results increases to ˆ= 1.2923. All radial functions in ͑6͒ are expanded into a series of the Ogilvie-Tipping variable z = x / ͑1+x /2͒ that remains finite −2 ഛ z Ͻ 2 throughout the whole range of the internuclear distance ͑0 ഛ R Ͻϱ͒.…”

“…56 In the above inequality i is the ith reduced residual and a i is the estimated accuracy of the measurement. All data which have not passed this test were excluded from the fit, and thus the original set of 183 transitions was reduced to a set of 145 transitions, including 23 pure rotational and 122 rotational-vibrational lines.…”

“…26 The relatively large HeH + permanent dipole moment has allowed highly precise measurements of vibrational-rotational and pure rotational gasphase spectra of this system and the determination of the transition energies. 18,[27][28][29][30][31][32][33][34][35][36][37][38][39] Among the first accurate experi-ments concerning the HeH + rovibrational spectrum, one should mention the work by Tolliver et al 28 and the works by Carrington et al 29,31 The latter group has observed vibrational-rotational lines of HeH + and its isotopic species near the dissociation limits. One should also mention the first direct infrared measurement of the absorption spectra of HeH + by Bernath and Amano 30 who measured nine transitions in the fundamental 1-0 band and determined molecular constants for the = 0 and = 1 vibrational states.…”