Mass spectrometric investigation of 2-methoxyethanol and 2-ethoxyethanol clusters: Magic numbers and structural implications

In this paper, we present the results of our mass spectrometric investigations for van der Waals clusters of 2-methoxyethanol and 2-ethoxyethanol. The cluster mass spectra were acquired for a variety of expansion conditions and electron energies. The protonated alkoxyethanol cluster ions {AE}_nH⁺ form the dominant cluster ion series. A number of fragment ions, that may arise from an unprotonated and/or a protonated alkoxyethanol molecular ion, were solvated by additional alkoxyethanol molecules. The {AE}_n{H₂O}_mH⁺ ions were observed with significant intensities only for n ≥ 5 in neat as well as mixed alkoxyethanol/water expansions. It was also found that {AE}_n{H₂O}_mH⁺ cluster ions which satisfy the condition n = 2 (m + 2), for m = 1 and 2, have enhanced ion intensities. Various models that may explain the behavior of {AE}_n{H₂O}_mH⁺ are discussed.