The excited electronic states of H2CSi

Abstract

Articles you may be interested inAnharmonic force field and vibrational dynamics of CH2F2 up to 5000 cm−1 studied by Fourier transform infrared spectroscopy and state-of-the-art ab initio calculations

Discovery of the optically forbidden S1–S transition of silylidene (H2C=Si)

“…First, the molecular parameters of the ground state were obtained by density functional theory ͑DFT͒ using the popular Becke three parameter hybrid density functional 25 and the Lee, Yang, and Parr correlation functional 26 ͑B3LYP͒, with the TZ(2d f ,2pd) basis set of Hilliard and Grev 9 and Dunning's correlation-consistent triple-and quadruple-zeta basis sets augmented by diffuse functions ͑aug-cc-pVTZ and aug-cc-pQTZ͒. 27 Comparisons with the known ground state geometry and vibrational frequencies of H 2 CSi and D 2 CSi showed that the B3LYP frequencies were generally closer to experiment than previous 9 CISD TZ(2d f ,2pd) values, due to the slightly longer bond lengths in the DFT calculations. The B3LYP method with the aug-cc-pVQZ basis set was then chosen for use in predicting the excited state vibrational frequencies.…”

“…Although the latter is forbidden, it gains intensity by the mixing of 4 1 and 6 1 , as discussed previously for the à -X transition. From ab initio predictions of the vibrational frequencies, 9 other vibration close to 4 Ј and 6 Ј is 3 Ј , and the c-type band has the correct polarization to be assigned as the transition to 3 1 . The SEP bands were surveyed to an energy of 17 370 cm Ϫ1 and the pattern of bands gets more complex until it becomes quite difficult to unravel, due to the multitude of interacting levels.…”

“…9 Assuming that the transition would borrow intensity from the strongly allowed B 1 B 2 -X 1 A 1 system at 340 nm, we would expect activity in the out-of-plane bending mode, 4 Ј , of b 1 symmetry, since the vibronic transition moment integral is should be prominent and, under jet-cooled conditions, these perpendicular bands would consist of three subbands (K a Ј -K a Љ :0 -1, 1-0, and 2-1 from lower to higher energy͒ with the central feature weaker than the outer two, due to the nuclear statistical weights. Careful examination of Fig.…”

“…Unlike vinylidene, silylidene is the global minimum on the SiCH 2 potential energy surface, [1][2][3][4][5][6][7][8][9] with the trans-bent silaacetylene species some 40-50 kcal/ mol higher in energy. This profound difference between the carbon and silicon compounds highlights the strong tendency of silicon to avoid multiple bonding, reflected in the fact that no carbon-silicon triply bonded molecules have yet been isolated.…”

Jet spectroscopy, structure, anomalous fluorescence, and molecular quantum beats of silylidene (H2C=Si), the simplest unsaturated silylene

“…On the basis of the previous experimental work of Leclerq and Dubois 4 and the ab initio results, 17 silylidene is a planar molecule of C 2 symmetry. The six fundamental modes of vibration are labeled 1 ͑a 1 , CH symmetric stretch͒, 2 ͑a 1 , CH 2 scissors͒, 3 ͑a 1 , CSi stretch͒, 4 ͑b 1 , out-of-plane bend͒, 5 ͑b 2 , CH asymmetric stretch͒, and 6 ͑b 2 , CH 2 rock͒.…”