Nanodiamonds (NDs) hosting nitrogen-vacancy (NV) centers are promising for applications of quantum sensing. Long spin relaxation times (T1 and T2) are critical for high sensitivity in quantum applications. It has been shown that fluctuations of magnetic fields due to surface spins strongly influence T1 and T2 in NDs. However, their relaxation mechanisms have yet to be fully understood. In this paper, we investigate the relation between surface spins and T1 and T2 of single-substitutional nitrogen impurity (P1) centers in NDs. The P1 centers located typically in the vicinity of NV centers are a great model system to study the spin relaxation processes of the NV centers. By employing high-frequency electron paramagnetic resonance spectroscopy, we verify that air annealing removes surface spins efficiently and significantly reduces their contribution to T1.
The recent detection of ethynyl-functionalized cyclopropenylidene (c-C 3 HC 2 H) has initiated the search for other functional forms of cyclopropenylidene (c-C 3 H 2 ) in space. There is existing gas-phase rotational spectroscopic data for cyanocyclopropenylidene (c-C 3 HCN), but the present work provides the first anharmonic vibrational spectral data for that molecule, as well as the first full set of both rotational and vibrational spectroscopic data for fluoroand chloro-cyclopropenylidenes (c-C 3 HF and c-C 3 HCl). All three molecules have fundamental vibrational frequencies with substantial infrared intensities. Namely, c-C 3 HCN has a moderately intense fundamental frequency at 1244.4 cm −1 , while c-C 3 HF has two large intensity modes at 1765.4 and 1125.3 cm −1 and c-C 3 HCl again has two large intensity modes at 1692.0 and 1062.5 cm −1 . All of these frequencies are well within the spectral range covered by the high-resolution EXES instrument on NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA). Further, all three molecules have dipole moments of around 3.0 D in line with c-C 3 H 2 , enabling them to be observed by pure rotational spectroscopy, as well. Thus, the rovibrational spectral data presented herein should assist with future laboratory studies of functionalized cyclopropenylidenes and may lead to their interstellar or circumstellar detection.
The ethynol (HCCOH) molecule has recently been shown to be present in simulated astrochemical ices possibly linking it to molecular building blocks for interstellar complex organic molecules like amino acids. The proposed reaction mechanism suggests the simultaneous formation of both ketene and ethynol from mixed carbon monoxide/water ice in simulated interstellar conditions. Rigorous anharmonic spectral data within both the IR and microwave regions are needed for possible detection of ethynol in the interstellar medium. This study provides the first such data for this molecule from high-level quantum chemical computations where experiment is currently lacking. Ethynol has a Beff comparable to, but distinct from acetonitrile at 9,652.1 MHz and three notable infrared features with two in the hydride stretching-regions and the C–C stretch at 2,212.8 cm−1. The ketene isomer has already been detected in the interstellar medium, and the possible detection of ethynol made possible by this work may lead to a deeper understanding of the proposed ice formation mechanism involving both species and how this relates to the molecular origins of life.
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