Infrared laser Stark spectroscopy of hydroxymethoxycarbene in 4He nanodroplets

Abstract

Hydroxymethoxycarbene, CH 3 OC OH, was produced via pyrolysis of monomethyl oxalate and subsequently isolated in 4 He nanodroplets.Infrared laser spectroscopy reveals tworotationally resolved a,bhybrid bands in the OH-stretch region, which are assigned totrans,trans-and cis,transrotamers. Stark spectroscopy of the trans,trans-OH stretch band provides the aaxisinertial component of the dipole moment, namely = 0.62(7)D. The computed equilibrium dipole moment agreeswell withthe expectation value determined from experiment, consistent with asemi-rigidCH 3 OC OH backbone computed viaa potential energy scan at the B3LYP/cc-pVTZ level of theory, which reveals substantial conformer interconversion barriers of 17 kcal/mol.

Infrared spectroscopy in superfluid helium droplets

“…than the energy of the thermally populated rotational states, so free rotation is replaced by libration of molecules around the electric field, which is described by motion in a parabolic potential [164,173,174]. The Stark spectra get more complex for open shell molecules, such as radicals [60,162,163,175,176]. One such example is that of hydroxyl radical (OH) which shows Ʌ-doubling of the Q(3/2) rotational branch [155].…”

“…Electric field study in helium droplets have also been employed for structure determination of molecular complexes, such as (HF) n [127], (H 2 O) m -(HCl) n [130], H 2 O clusters [187], and others [183,184,188]. VTMA was also instrumental in determination of the structure and spectral assignment of pre-reactive complexes [162,163,175,176,178].…”

Infrared Spectroscopy of Molecular Radicals and Carbenes in Helium Droplets

“…Hydroxymethoxycarbene (CH 3 O COH) was similarly produced via monomethyl oxalate pyrolysis [36]. Two rotationally resolved a,b-hybrid bands in the OH-stretch region were assigned to trans,trans-and cis,trans-rotamers.…”