Spectroscopy of the transition of formaldehyde in the 30140–30790cm−1 range: The and rovibrational bands

Motsch, Michael; Schenk, Markus; Zeppenfeld, Martin; Schmitt, Michaël; Meerts, W. Leo; Pinkse, Pepijn W. H.; Rempe, Gerhard

doi:10.1016/j.jms.2008.06.002

Cited by 10 publications

(32 citation statements)

References 40 publications

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“…The only pure valence transition n À p Ã ( 1 A 2 ) observed in this molecule lies at 4.02 eV. [8,21] From the experimental spectrum and its assignments, we are able to identify three weak progressions at 7.086, 7.728, and 8.593 eV indicated in Table 1 as A, E, and B. [17,25] The intense narrow absorption peak at 7.086 eV corresponds to the 0 À 0 band assigned to the first member of the n À 3 s (r) Rydberg series, and the vibrational structure could be assigned to the three symmetric modes Synchrotron Radiation at Indus I n 1 ¼ 2560 cm À1 , n 2 ¼ 1590 cm À1 , n 3 ¼ 1210 cm À1 and the n 4 out-of-plane bending anharmonic mode, which is associated with an inversion manifold of $346 cm À1 .…”

Section: Resultsmentioning

confidence: 80%

“…[7] The electronic spectrum of HCHO has been investigated extensively since the 1930s, focusing on its Rydberg and intravalence transitions. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] The electronic spectrum in the vacuum-ultraviolet (VUV) region ($7-11 eV) was recorded by both electron impact and optical techniques. [16,17] Further the photoabsorption spectra that were measured using dipole (e,e) spectroscopy in the photon energy region 3-200 eV were used to calculate absolute oscillator strengths by method of Cooper et al [19] In spite of the size and simplicity of formaldehyde, assignments of the Rydberg and valence states were found difficult because of strong interactions between them.…”

Section: Introductionmentioning

confidence: 99%

“…[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Most of these calculations, which focus on different aspects such as geometrical structure, vertical and adiabatic excitation energies, and frequencies of excited states, have been reviewed by Jose et al [39] It may be seen from literature that the only strong valence transition observed is from the ground state to the first excited singlet state in 4.08 eV region assigned to the Ã 1 A 2 ÀX 1 A 1 band system and that it consists of an extended progression of vibronic bands. [8,21] Some of the Rydberg states are well located, but there is ambiguity in respect of the vertical ordering of some low-lying Rydberg transitions, viz 1 B 2 (n-3p z ), 1 A 1 (n-3p y ), and the absence or weak structures of other excited valence states, viz 1 A 1 (p À p Ã ), 1 B 1 (r À p Ã ), that are expected to lie in the same energy region. [37,[40][41][42] Other Rydberg series converging to electronically excited states of HCHO þ calculated by Pablo et al [43] have been interpreted as consisting exclusively of Rydberg transitions converging to the ground state of HCHO þ with the vertical ionization potential (IP) of 10.884 eV.…”

Section: Introductionmentioning

confidence: 99%

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Photo-Absorption Studies on Formaldehyde Using Synchrotron Radiation at Indus I

Krishnakumar

Rajasekhar

Saraswathy

et al. 2012

Spectroscopy Letters

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Photo-absorption spectra of formaldehyde (HCHO) is recorded in the range of 6-11.5 eV at various pressures (<0.001-2 mbar) at an average resolution of 1.2 Å using Photophysics beam line at the 450 MeV Indus-1 synchrotron radiation facilities at RRCAT Indore, India. The spectrum is found to consist exclusively of n ! Rydberg transitions converging to the ground state of HCHO þ . The highest identified Rydberg states, observed up to the first ionization limit of HCHO, correspond to 7s, 11p, 9d, and 12f orbitals. Analyzed electronic spectrum along with the intensities and quantum defects are presented. To interpret the observed weak valence transitions instead of strong valence transitions, a theoretical study of Rydberg and valence electronic states of HCHO is performed in the framework of single configuration interaction (CIS) and time-dependent density functional theory (TDDFT) using different basis sets. Electronic transition energies of high-lying singlet and triplet valence states as calculated using TDDFT (B3LYP) level of theory are found to give fairly-good agreement with the experimental data.

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Section: Resultsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photo-Absorption Studies on Formaldehyde Using Synchrotron Radiation at Indus I

Krishnakumar

Rajasekhar

Saraswathy

et al. 2012

Spectroscopy Letters

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“…Even though the basic kinematics are very well understood it is far from trivial to predict the motion of an individual molecule inside a guide, let alone the velocity-dependent transmission of an entire thermal ensemble of molecules, even through a passive device like a guide [43,44,[78][79][80]. In the simplest cases of straight or bent multipole guides fabricated from single-piece electrodes (or magnets) the transmission can be estimated based on simple formulae like equation 3.…”

Section: Trajectory Simulationsmentioning

confidence: 99%

Merged neutral beams

Osterwalder

2015

EPJ Techn Instrum

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A detailed description of a merged beam apparatus for the study of low energy molecular scattering is given. This review is intended to guide any scientist who plans to construct a similar experiment, and to provide some inspiration in describing the approach we chose to our goal. In our experiment a supersonic expansion of paramagnetic particles is merged with one of polar molecules. A magnetic and an electric multipole guide are used to bend the two beams onto the same axis. We here describe in detail how the apparatus is designed, characterised, and operated.Keywords: Cold molecules; Low energy scattering; Molecular beams; Cold chemistry ReviewIn the last 15 years several methods have been developed to prepare molecular samples at temperatures well below 1 K and to completely control their translational degrees of freedom [1][2][3][4]. A particular area where this is of interest is the study of molecular collisions, and cold chemistry [4][5][6][7][8][9][10][11]. Ultracold molecules, produced by joining two atoms at very low temperature, enabled the investigation of molecular collisions at temperatures as low as 1 μK [12][13][14]. These methods are ideally suited to study alkali dimers, but in order to access broader classes of molecules and a larger range of temperatures a different approach was necessary. The present paper describes such an approach, namely the merging of two molecular beams with controlled velocity.One of the most important developments for reaction dynamics studies in the twentieth century was the crossed-beam technique, for which a Nobel prize was awarded in 1986. In this experiment two molecular beams [15] are crossed to enable a highly detailed investigation of gas-phase molecular scattering, and in particular the measurement of state-to-state differential cross sections [16,17]. The high velocities of supersonic expansions and the crossing angle of usually 90 degrees make the crossed beam technique ideal for studies at high collision energies (E/k B 100 K, where k B is the Boltzmann constant). Lower energies are not accessible without special modifications, thus making the method blind to some of the most fundamental quantum mechanical effects in molecular scattering.The collision energy in a crossed beam experiment depends on the relative velocity of the two reactants. In any molecular collision event the energetics are given only by the motion in the molecular frame of reference (MFR), but not that of the centre of mass (CM). This is illustrated in Fig. 1. Panel A shows the position vectors for reactants 1 and 2

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“…This inner product has it maximum if the two spectra are identical. Various EA strategies have been developed and tested for their robustness in dealing with high resolution spectra including Laser Induced Fluorescence, 2,3 FTIR spectroscopy, 4 Room temperature UV absorption spectroscopy 5 and NMR spectroscopy. 6,7 While the application of EAs to analyze rotationally-resolved spectra has been successfully demonstrated for a range of spectroscopic techniques, it has not yet been tested for high resolution room temperature FTIR spectra.…”

Section: Introductionmentioning

confidence: 99%