M. Eliades

Rotational‐vibration analysis of the n=0, nν6+ν1−nν6 subband in the hydrogen‐bonded system 16O 12C ⋅⋅⋅ 1H 19F

Thirty‐three P(J) branch and 15 R(J) branch transitions associated with the n=0, nν6+ν1−nν6 vibration in 16O 12C ⋅⋅⋅ 1H 19F have been assigned. Rotational constants B, centrifugal distortion constants DJ, rotational‐vibrational interaction constant α1, and the frequency of the band origin ν0, have been determined as: B″=0.102 148(14)cm−1; B′=0.104 196(14) cm−1; D″J=3.6(1.8)×10−7 cm−1; D″J=3.8 (1.8)×10−7 cm−1; α1=−61.4(5) MHz; ν0=3844.0294 (50) cm−1. The spectrum is consistent with a linear complex having a hydrogen bond ν6 bending frequency of 75±12 cm−1 and excited state r(C⋅⋅⋅F) distance of 3.012 A. A lower limit to the excited state lifetime is set at ≥2.8×10−10 s.

The gas phase infrared spectrum of ν1 and ν1−ν4 HCN‐‐‐HF

A continuously tunable single frequency color center laser has been used to investigate the rovibrational static gas phase infrared spectra of the ν1 (H–F stretching vibration) and its hot bands ν1+ν17 −ν17 and ν1+ν4−ν4 in the linear dimer HCN‐‐‐HF. Observed perturbations in the ν1 and ν1+ν17 −ν17 subbands results from Coriolis interactions of the excited vibrational states ν1 and ν1+ν17 with ν2+2ν4+ν17 and ν2+2ν4+2ν07 , respectively. The influence of Coriolis interactions and vibrationally predissociating excited state lifetimes of 1.06(10)×10−10 s are considered in simulation of the observed band profiles. Molecular and anharmonic cross term parameters associated with investigated vibrational states are also presented. Anharmonic crossterms X○14 , X○17 , and X○47 are evaluated as 8.0252(73), 4.2162(53), and 1.000(49) cm−1, from the available data, including the analysis from the unresolved spectra of ν1−ν4 and ν1−ν4+ν17 −ν17 . The differences of the band origins in ν1 and ν1−ν4 give a value of ν4=168.34...

Preliminary Rovibrational Analysis of the nν6+ν1−nν6 Vibration in HCN⋅⋅⋅HF

A preliminary rotation‐vibration analysis of the n=0 and n=1 subbands associated with the nν6+ν1−nν6 hydrogen‐bonded vibration in HCN⋅⋅⋅HF has been completed. The following excited state rotational constants B′ and band origin frequencies ν0 have been determined for the complex. The results are consistent with a rotation‐vibration interaction constant α1=−68.3±1 MHz which correlates with an excited state r(N⋅⋅⋅F) internuclear distance of 2.762 A, a decrease of 0.034 A relative to the ground state. Excited state lifetimes associated with assigned transitions are demonstrated to be ≥1.8×10−10s while the x16 anharmonic constant is evaluated to be 4.01±0.03 cm−1.

Determination of dissociation energies and thermal functions of hydrogen‐bond formation using high resolution FTIR spectroscopy

A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bond dissociation energies D0 and De. Results for HCN‐‐HF give a D0=20.77(22) and De =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and ab initio molecular orbital calculations. Rovibrational band information available for HCN‐‐HF also permits evaluation of thermal functions of dimer formation in kJ/mol: ΔU○298.2 =20.1(2), ΔH○298.2 =22.6(2), ΔG○298.2 =59.4(2), ΔS○298.2 =−0.1235.

Color center laser spectroscopy of ν2 HCN‐‐‐HF

A continuously tunable single frequency color center laser spectrometer has been applied to analyze the rovibrational gas phase spectra of the fundamental ν2 (C–H stretching vibration) and its hot bands ν2+ν4−ν4 and ν2+ν17−ν17 in the linear dimer HCN‐‐‐HF. The l‐type doubling constants q″v and qv of the Π←Π band are both determined to be 12.4(8) MHz and anharmonic cross terms X024 and X027 are evaluated as −0.1656(17) and +0.1310(35), respectively from the available data. Excited state amplitude lifetimes in the ν2 band are demonstrated to be 1.3(4)×10−8 s.

cw planar supersonic jet spectroscopy of ν2 OCHCl using a computer-controlled tunable diode laser

Abstract Rovibrational analysis of ν 2 OCHCl is reported in a cw supersonic jet using a computer-controlled tunable infrared diode laser spectrometer. The following fitted molecular parameters were determined (in cm −1 ): for OCH 35 Cl: ν 2 = 2155.499915(27), B 2 = 0.05548062(22), D J (2) = 1.608(3) × 10 −7 , B 0 = 0.05576299(2), D J (0) = 1.6004(25) × 10 −7 ; and for OCH 37 Cl: ν 2 = 2155.505054(40), B 2 = 0.05420894(30), D J (2) = 1.550(4) × 10 −7 , B 0 = 0.05448403(2), D J (0) = 1.5294(30) × 10 −7 . Observed transitions in both isotopic species are consistent with excited state lifetimes greater than 0.64 ns and no rotational dependence was discerned.

Supersonic molecular beam and static gas phase spectroscopy of intermolecular hot bands associated with ν1 16O12C---1H19F

Abstract Gas phase rovibrational analysis of the ν1 (H stretching vibration) and its associated hot bands ν1+ν3−ν3, ν1 + ν51−ν51 and ν1 + 2ν5, −2ν5 are investigated using a broadband tunable color center laser spectrometer. Rotational and distortion constants associated with the low frequency intermolecular stretching (ν3) and bending (ν51) states are determined to be for ν3:B=0.100786(28) cm−1, DitJ=3.36(30)×10−7 cm−1; and for ν51: B=0.1029736(93) cm−1, DJ=3.598(41)×10−7 cm−1q=0.000235(15) cm−1. The precisely evaluated band origin frequencies permit determination of two anharmonic cross terms associated with the hydrogen bond hypersurface x13 = 8.634(20) and x15 = 5.4099(6) cm−1.

A cw planar jet computer‐controlled tunable IR diode laser spectrometer for the investigation of hydrogen‐bonded complexes

An ultrasensitive computer‐controlled tunable infrared diode laser cw planar supersonic jet spectrometer for second derivative detection of hydrogen‐bonded complexes is described. Spectroscopic analyses of transitions in carbon monoxide monomer permit detection limits to be set at 2.9×106 molecules/cm3/quantum state. Simultaneously recorded spectra of the ν2C≡O stretching vibrations in OC—HCl and OC—HBr are presented to illustrate the performance of this supersonic jet spectrometer for investigating weakly bound hydrogen‐bonded dimers.

Gas-phase rovibrational analysis of v1 HCN---H35Cl

Abstract A continuously tunable single-frequency color-center laser spectrometer has been used to rovibrationally analyze the static gas-phase spectrum of the v 1 (C-H stretching) vibration in HCN---H 35 Cl providing molecular parameters: v 1 = 3309.0286(3) cm −1 , B 1 = 2007.37(36) MHz and D j 1 = 3.51(13) × 10 −3 MHz and a lower limit of 1 × 10 −9 s to the v 1 3 excited state lifetimes. Possible assignments for the hot band progressions and are also discussed.

Simple color center laser optothermal molecular beam spectrometer for high‐resolution infrared spectroscopy

A broadband tunable single‐frequency color center laser optothermal molecular beam spectrometer has been constructed. K components have been resolved for P(18) to R(11) rovibrational transitions in ν1 CH3C≡C–H. The observed transition linewidths are demonstrated to be ≤6 MHz and are determined with a relative precision of ≤10 MHz over the 15‐cm−1 frequency segment scanned.