High-resolution infrared spectra of vibrationally excited HC4H in a supersonic hydrocarbon plasma jet

Theoretical investigation of the infrared spectrum of small polyynes

“…90 Diacetylene shows a similar 0.2% difference between the theoretical value of B 0 = 0.146167 cm À1 , and the experimentally determined value of B 0 = 0.1464123(17) cm À1 . 50 The consistent accuracy of these values suggests that the method presented is clearly good enough to be extrapolated to and aid high-resolution infrared spectroscopic searches for the larger polyynes.…”

“…The vibration-rotation interaction constants (Table 4) are also determined in the course of the VPT2 calculation, and are in good agreement with both previous theoretical studies 52,54 and experimentally determined values. 29,44,46,50,51,54 Based on the vibration-rotation interaction constants, the ground state rotational constants (B 0 ) were determined using the AE-CCSD(T)/ cc-pCVQZ determined B e values ( Table 1). For acetylene, B 0 = 1.175319 cm…”

“…11,12,20,21 However, accurate line positions for tetraacetylene are lacking, from either laboratory or theoretical studies. Extensive theoretical and experimental studies have been carried out for acetylene and diacetylene in the past few decades, including high-resolution spectroscopic studies of all the fundamental bands and a significant number of the combination bands, 29,[40][41][42][43][44][45][46][47][48][49][50] and high level ab initio calculations that take into account anharmonic effects. [51][52][53][54] The combination of these studies shows that current quantum chemical theory, particularly coupled cluster theory with single and double excitations and augmented by a perturbative treatment of triple excitations (CCSD(T)), 55 is able to accurately reproduce equilibrium geometries, experimental vibrational frequencies, vibration-rotation interaction constants (a i ), and ground state rotational constants (B 0 ).…”

“…64 While the two modes that are most useful for astronomical identification (n 14 and n 10 + n 14 ) were measured, the uncertainty associated with the line positions is too large to allow for an unambiguous assignment. Moreover, some high-resolution IR searches have been attempted, 50,61,62,67 but so far no transitions have been assigned to tetraacetylene. In this paper, we report the ab initio calculations for acetylene, diacetylene, triacetylene, and tetraacetylene.…”

High-resolution infrared spectrum of triacetylene: The ν5 state revisited and new vibrational states

“…Certain vibrational modes will induce a temporary dipole moment that can be detected as ro-vibrational spectra in the mid-and 20 far-infrared. While, the spectroscopic information of both acetylene and diacetylene has been studied in detail in laboratory studies facilitating their detection (see Zhao et al [22] and Chang and Nesbitt [23] and references therein), the spectroscopic information for triacetylene so far has remained limited. Vibrational frequencies for the fundamental bands of triacetylene, Table 1, have been known with a resolution of 1 cm −1 [24], but high-resolution rotational information is only known for about half of the modes: ν 5 , ν 6 , ν 8 , ν 10 , ν 11 , and ν 13 [25,26,27,28]; it is noted that ν 8 and 25 ν 10 rotational information is determined from the 8 1 0 11 1 0 combination band and the 8 1 0 11 1 0 10 1 1 and 11 1 0 10 1 1 hot bands, respectively [25].…”