Infrared absorption of t -HOCO + , H + (CO 2 ) 2 , and HCO 2 - produced in electron bombardment of CO 2 in solid para -H 2

Prasanta Das, Masashi Tsuge, Yuan-Pern Lee*

*Corresponding author for this work

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Abstract

We have employed electron bombardment during matrix deposition of CO 2 (or 13 CO 2 , C 18 O 2 ) and para-hydrogen (p-H 2 ) at 3.2 K and recorded infrared (IR) spectra of t-HOCO + , H + (CO 2 ) 2 , HCO 2 - , CO 2 - , t-HOCO, and other species isolated in solid p-H 2 . After the matrix was maintained in darkness for 13 h, intensities of absorption features of t-HOCO + at 2403.5 (ν 1 ), 2369.9 (ν 2 ), 1018.1 (ν 4 ), and 606.5 (ν 6 ) cm -1 and those of H + (CO 2 ) 2 at 1341.1, 883.6, and 591.5 cm -1 decreased. Corresponding lines of isotopologues were observed when 13 CO 2 or C 18 O 2 replaced CO 2 . In contrast, lines of HCO 2 - at 2522.4 (ν 1 ), 1616.1 (ν 5 ), 1327.9 (ν 2 ), and 745.6 (ν 3 ) cm -1 increased in intensity; corresponding lines of H 13 CO 2 - or HC 18 O 2 - were also observed. Lines of t-DOCO + and DCO 2 - were observed in an electron bombarded CO 2 /normal-deuterium (n-D 2 ) matrix. Data of ν 6 of t-HOCO + and all observed modes of H 18 OC 18 O + and HC 18 O 2 - are new. The assignments were made according to expected chemical behavior, observed isotopic shifts, and comparisons with vibrational wavenumbers and relative intensities of previous reports and calculations with the B3PW91/aug-cc-pVQZ method. The ν 1 line of t-HOCO + in solid p-H 2 (2403.5 cm -1 ), similar to the line at 2673 cm -1 of t-HOCO + tagged with an Ar atom, is significantly red-shifted from that reported for gaseous t-HOCO + (3375.37 cm -1 ) due to partial proton sharing between CO 2 and H 2 or Ar. The ν 1 line of HCO 2 - in solid p-H 2 (2522.4 cm -1 ) is blue shifted from that reported for HCO 2 - in solid Ne (2455.7 cm -1 ) and that of HCO 2 - tagged with Ar (2449 cm -1 ); this can be explained by the varied solvation effects by Ne, Ar, or H 2 on the mixing of H + + CO 2 and H + CO 2 - surfaces. Possible formation mechanisms of t-HOCO + , H + (CO 2 ) 2 , HCO 2 - , CO 2 - , t-HOCO, H 2 O, and t-HCOOH are discussed.

Original languageEnglish
Article number014306
JournalJournal of Chemical Physics
Volume145
Issue number1
DOIs
StatePublished - 7 Jul 2016

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