The Vibrational Constants of Acetylene

Abstract

On the basis of the work done by Darling and Dennison on the water vapor molecule, the vibrational constants of acetylene are calculated, taking into account the resonance interaction arising from the near equality of the fundamentals ν1 and ν3. Seventeen band centers are known experimentally. The band centers depend on the 10 constants χi, χik and γ which are functions of the potential constants. The expressions for the vibrational energies of the band centers are set up, those for interacting doublets or triplets being found by perturbation methods. The 10 constants are determined and the positions of eight bands calculated to check the results. The agreement is very satisfactory. The positions of 10 other bands not yet observed are predicted.

Infrared spectrum of acetylene

“…It is c ustomary to expr ess the vibraLion al energy in terms of th e vibrational q uan tum numbers as [7] and shown to exist. Such a r esonance introduces a not hcr constant, 1', to b e evaluated.…”

Infrared Spectroscopy

“…The theoretical papers include studies on cis-trans isomerism (as), identical atomic groups (46), homonuclear molecular absorption induced by intermolecular forces (51,19.6,263), forces and force constants (130,159,160,235,247,248,250), integrals useful in molecular orbital calculations (195), redundant coordinates (239), electronic states of conjugated systems (45, 249), interaction terms (67, 149,159), acyclic molecules (59), degenerate fundamentals (60), the asymmetric rotor (89, 98), condensed systems (the solid state) (267), internal rotation (129, 135, 150,182,184,185), the iteration method of solving secular equations (143), the planar X Y 3 molecule ( l o g ) , the tetrahedral anions (110) 203,204, 261), ethylene, including halogenated (68, 145, 146, 158, 261), acetylene and methyl acetylene (175,176,192,271,ZTS), allene (113), ketene (65), hydrogen halides (57,193,260), dimethyl cadmium, mercury and zinc (96,97), ethylene oxide ( formaldehyde (158), thiophene (1 62), arsine and deuteroarsine (163,164), acetaldehyde (198), oxygen fluoride ( Am., 39, 402 (1949). (80) Gates, D. M.. J .…”

“…The specific molecular studies include papers on the following: hydrocarbon molecules in general (44, 80, 82-85, 228, 234), benzene (16,49,50), methane (38,114,161,189,238,244,256), halogenated and deuteromethane, the deutero ammonias (39), ethane, including halogenated and deuteroethane (24,25,27,69,183,201,224,235), propane, including deuterated (78, 168), secbutyl alcohol (26), boron compounds (47,203,204,261), ethylene, including halogenated (68,145,146,158,251), acetylene and methyl acetylene (175,176,192,271,273), aliene (113), ketene (65), hydrogen halides (57,193,260), dimethyl cadmium, mercury and zinc (96, 97), ethylene oxide (86,259), carbon monoxide (115,147), carbon dioxide (222), carbonyl fluoride (270), hydrogen cyanide (116), malonitrile (100), ethyl alcohol (99), chlorine trifluoride (121), tritium deuteride (127), urea (131), the octenes (140), formaldehyde (158), thiophene…”

Vibrational constants of acetylene-d2

“…Unfortunately, the constants they deduced do not satisfactorily account for the frequencies in the photograpbic region. It is believed that the difficulty arises from a second-order resonance due to the near equality of VI and V3, because such an effect has been found in the spectrum [3] of C2H z. F ur t hermore, a new analysis of the band, VI-V~, near 2,167 cm-I places this band center one line spacing higher than the previous work [4]. As the deLermination of the freque ncy of VI, which is not active in theinfr arecl, depends d irectly on th e frequency of tbis band, a new band center for this band leads to a new freq uency for VI.…”

“…The theory of this second-order resonance has been worked out adequately and is in the literature [3,8].…”