The valence shell electronic states of trimethylene oxide studied by photoabsorption andab initiomultireference configuration interaction calculations

Ring-Puckering Effects on Electron Momentum Distributions of Valence Orbitals of Oxetane

“…Oxetane has been studied by high resolution photoelectron spectroscopy (PES) utilizing He I ultraviolet [30][31][32] and synchrotron radiations. 33 The most recent He I PES result 32 is shown in Figure 3(a) for comparison.…”

“…26 Therefore the ring of the molecule can essentially be regarded as planar (C 2v ). [30][31][32][33] The TMPs calculated at planar geometry (solid curves) generally reproduce the XMPs except HOMO where the TMP at C 2v geometry completely fails to interpret 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 12 the large "turn-up" at low momentum region (see Figure 4). In fact, the ring of oxetane molecule is actually puckered.…”

“…26 Therefore the ring of the molecule can essentially be regarded as planar. [30][31][32][33] Meanwhile, the frequency of the ring puckering vibration is sufficiently low so that many excited vibrational levels in this mode are appreciably populated at room temperature. 24,[27][28] Recent EMS studies by Miao et al 34 and Watanabe et al 35 showed that the EMDs of the valence orbitals can be affected noticeably by the vibrational motions.…”

“…It is quite unusual for the oxetane molecule that the lowest vibrational level lies 11.86 ± 0.05 cm –1 above the top of the barrier . Therefore, the ring of the molecule can essentially be regarded as planar. − Meanwhile, the frequency of the ring-puckering vibration is sufficiently low so that many excited vibrational levels in this mode are appreciably populated at room temperature. ,, Recent EMS studies by Miao et al and Watanabe et al showed that the EMDs of the valence orbitals can be affected noticeably by the vibrational motions. In line with this idea, it is possible to investigate the ring-puckering effect on the EMDs for oxetane by taking into account the thermally populated vibrational states of the ring-puckering.…”

Vibrational Effects on Electron Momentum Distributions of Outer-Valence Orbitals of Oxetane

“…Oxetane or trimethylene oxide, a four-membered ring molecule of flexible structure, is one of the simplest molecules having ring-puckering motion. − The unusual one-dimensional ring-puckering potential curve is proved to be a double-minimum function with an extremely low barrier of 15.52 ± 0.05 cm –1 , and the first vibrational level is only 11.86 ± 0.05 cm –1 above the barrier in the electronic ground state . Though oscillating between two equivalent bent conformers, oxetane can essentially be treated as a planar ring molecule ( C 2 v ). − On the other hand, many excited vibrational levels in this mode are appreciably populated at room temperature because the frequency of the ring-puckering vibration is sufficiently low . Recently, Yang et al reported their EMS study on five outer-valence molecular orbitals (MOs) of oxetane.…”