Spectrum Of H3 Research Articles

Investigation of non-adiabatic effects for the ro-vibrational spectrum of H3+: the use of a single potential energy surface with geometry-dependent nuclear masses

ABSTRACTThe influence of non-adiabatic effects on the ro-vibrational bound states of H+3 has been investigated using geometry-dependent reduced masses and only one single potential energy surface. The used potentials (BO electronic energy, adiabatic corrections and relativistic contributions) are based on explicitly correlated wavefunctions. For the first time, several different fully geometry-dependent reduced mass surfaces in three dimensions have been incorporated for the vibrational and rotational contributions.

The vibration-rotation spectrum and anharmonic potential of H3+

Some qualitative effects of anharmonicity on the spectra of H 3 + and D 3 + between low vibrational levels are described. Using large-basis vibration-rotation calculations with a Morse-based discrete variable representation for the vibrations and a symmetric-top basis for the rotations, new spectra of H 3 + and D 3 + have been assigned. This procedure was assisted by adjusting eight coefficients for H 3 + and six coefficients for D 3 + in the Meyer-Botschwina-Burton ab initio potential function, and eventually 621 new and old lines of H 3 + to levels up to 3 ν 2 and 529 new and old lines of D 3 + to levels up to 2 ν 2 have been fitted with standard deviations of 0.118 and 0.059 cm −1 , respectively. An attempt is made to compare five different potential energy functions for the H 3 + system, two ab initio and three adjusted to fit spectra of H 3 + or D 3 + , by expanding them by the same procedure in the same variables. For extension of the present work to higher vibrational levels, more accurate boundary behaviour at linear configurations will be required, and some aspects of the use of hyperspherical coordinates are discussed.

Calculated rotational and rovibrational transitions in the spectrum of H3(+)

New calculations of line strengths and transition frequencies for the forbidden rotational spectrum and the nu2 fundamental rovibrational band of H3(+) are presented. These first principles calculations use the highly accurate ab initio electronic potential energy surface of Meyer, Botschwina, and Burton (1986), which has previously been shown by the authors to give rovibrational transition frequencies, rotational constants and vibrational fundamentals of spectroscopic accuracy. The line strengths calculated for the pure rotational spectrum in the vibrational ground state are in general agreement with those previously predicted by Pan and Oka (1986), although individual line strengths may differ by as much as 50 percent. The data are presented to assist with the interstellar detection of this astrophysically important molecular ion. 25 references.