Rotationally resolved IR spectroscopy of hexamethylenetetramine (HMT) C₆N₄H₁₂

Abstract

Context. Hexamethylenetetramine (HMT) appears to be a potential constituent of several objects in space, including comets or Titan's atmosphere and, as an organic residue of ice irradiation in the laboratory, it may be present in the interstellar medium. Aims. We performed a laboratory study of rotationally resolved intense IR bands of HMT to provide accurate line positions and synthetic spectra to be used for potential astronomical detections. Methods. We used synchrotron-based high-resolution Fourier transform infrared spectroscopy to record the experimental data. A formalism and programs dedicated to the assignment, analysis, and simulation of absorption spectra of tetrahedral molecules were used to exploit the spectra. Results. Infrared spectra of gas phase HMT were recorded and accurate wavenumbers and molecular parameters for four intense bands located in the 1000-1500 cm −1 spectral range suitable for astronomical searches were derived.

Path to achieving molecular dispersion in a dense reactive mixture

“…The literature provides guidance for their assignments. 36 As shown in Figure 11, the totally degenerate CAN stretching vibration for crystalline HMTA is observed at 1235 cm 21 . In this case, the CAN stretching vibration undoubtedly is also perturbed by various secondary forces.…”

“…The isolated CAN stretching vibration can only be found for HMTA in the upper atmosphere and is located above 1240 cm 21 . 36 Therefore, when hydrogen bonds form, it is expected that CAN stretching should shift downwards. Based on these previous assignments, we have assigned the 1239 cm 21 component as associated with isolated HMTA and the peak at 1233 cm 21 to the hydrogen-bonded CAN of the HMTA molecule.…”

Synchrotron-based Fourier transform spectra of the ν23 and ν24 IR b

“…In the present case, as in Ref. [5], the GS effective Hamiltonian was expanded up to order zero only, which implies a single term, that is B 0 J 2 . We thus used here the same calculated ground state rotational constant value (B 0 ¼ 0:0624482 cm À1 ) as in this previous work.…”

“…After the pioneering work of Hewett et al [1] using a molecular beam, the advent of synchrotron-based FT spectroscopy permitted to extend the study of rotationnally resolved IR bands of small Polycyclic Aromatic Hydrocarbons (PAHs) such as naphthalene and its derivatives (see e.g. [2,3] and references therein) and diamondoid-like molecules [4,5]. Hexamethylenetetramine (or HMT), C 6 N 4 H 12 , is strongly suspected to be present in several astrophysical objects such as e.g.…”

“…Only nine triply degenerate modes of F 2 symmetry are IR active from the ground state (GS, A 1 symmetry). In a previous article we reported a study containing the rotational analysis of the Since most of the experimental and analysis procedures have already been detailed in our earlier paper [5], we limit the present article to specific details of the m 24 -GS and m 23 -GS bands.…”