Hydrogen photoelectron spectra

The timescale of a microwave observation is ca 10 12s so that an average of the properties of the species in equilibrium (35) is obtained if the equilibrium occurs in a time shorter than this. The X-ray photoelectron spectra of intramolecularly hydrogen-bonded species in the gas phase have been studied in an attempt to obtain an instantaneous picture of the structure of these molecules. In this technique the ionisation of core electrons which occurs within 10 16s is observed. For malondialdehyde, 6-hydroxy-2-formyl-fulvene, 2-hydroxy-1,1,1,5,5,5-hexafluoropent-2-ene-4-one, 9-hydroxyphen-alenone [19], and tropolone [20], two peaks are observed in the Ou region of the photoelectron spectrum (Brown et al., 1979). If these molecules existed in the C2v form with a symmetrical hydrogen bond and equivalent oxygen... 

A considerable amount of the strain in l,8-bis(dimethylamino)naphtha-lene is relieved by protonation and the N—H N bond length (260 pm) in the protonated amine shows that the molecule is able to adopt a conformation [55] with an intramolecular hydrogen bond (Truter and Vickery, 1972). The infra-red spectrum of protonated l,8-bis(dimethylamino)naphthalene and the chemical shift (5 19.5) of the acidic proton in the nmr spectrum confirm the presence of an intramolecular hydrogen bond (Alder et al., 1968). The magnitude of the isotope effect on the chemical shift (Altman et al., 1978) and the appearance of two Nls peaks in the photoelectron spectrum... 

SF-OD level with the basis set composed of a cc-pVTZ basis on carbons and a cc-pVDZ basis on hydrogens). These energies are very close to the MRPT values (26) of 0.72 and 0.83 eV (for the 1 fi and 1 Ai states, respectively). With regard to experiment, the lowest adiabatic state, 1 B, has not been observed in the photoelectron spectrum (40) because of unfavorable Frank-Condon factors. The experimental adiabatic energy gap (including ZPE) between the ground triplet state and the VA state is 0.70 eV. The estimated experimental >s 0.79 eV, which is 0.15 eV lower than the SF-OD estimate. 

The VSEPR assumption that there are four identical localized electron pair bonds in the four C-H regions, made up from sp3 hybrid carbon orbitals and the hydrogen Is orbitals, is not consistent with the experimentally observed photoelectron spectrum. The MO theory is consistent with the two ionizations shown in the photoelectron spectrum of CH4 and implies that the bonding consists of four electron pairs which occupy the la, and It, five-centre MOs. 

Figure 1. Photoelectron spectrum of hydrogen peroxide as obtained hy Kimura and Osafune.

Fig. 37. Photoelectron spectra of V20s(001) and VO2 H0)/TiO2(110) in comparison with a photoelectron spectrum obtained after dosing atomic hydrogen to a V205(001) surface.

The photoelectron spectrum and ab initio SCF calculations of sulphur dichloride have been presented, and an assignment of observed states of the SCF radical cation was attempted.71 For the SC12 ground state the calculated dissociation energy, dipole moment, total atomic population, and total d -orbital population were given. The photolysis of sulphur monochloride with a series of saturated aliphatic hydrocarbons has been shown to yield alkyl chlorides, di- and poly-sulphides, hydrogen chloride, and elemental sulphur.72... 

Halothane (whose photoelectron spectrum was measured previously by Turner et al. p. 242) has the Br bands at 11.24 and 1T45, the Q bands at 12.20 and 12.32 eV showing that the interaction between the Br and Cl lone pairs is not strong. This is another case of a molecule having both an acidic hydrogen and a low IP and a high anesthetic potency. 

In the rest of this section we discuss our analysis (10,11) of the accurate cumulative reaction probabilities for the halogen-hydrogen halide systems that were published by Schatz (17-19). The CRPs were digitized with an optical scanner, which introduces negligible error. The accurate N°(E) was fit with cubic splines and convoluted using Eq. (20). Our analysis is based on the observation that the calculated CRPs of Schatz for Cl + HC1,1 + HI, and I + DI appeared to have an overall steplike structure reminiscent of that associated with quantized transition states, underlying the narrower features associated with trapped-state resonances and rotational thresholds. Our conclusion that quantized transition states exert broad control of the chemical reactivity for these reactions is not inconsistent with Schatz s description of the narrow trapped-state resonance and rotational threshold features. These different sorts of dynamical features represent different time scales, with the shorter-time (broader) features being more closely related to the traditional concern of chemical kinetics, i.e., reactivity, as discussed below Eq. (23). The relationship of features in the CRP to features in the photoelectron spectrum is not fully worked out yet. 

Fig. 1. Typical ATI photoelectron spectrum obtained from hydrogen Is with an infrared laser radiation pulse (see text). Here, the spectrum is derived from the occupation density of the atomic positive energy states, as computed after the laser pulse.

There is first the fundamental of a strong infrared laser. For the sake of illustration, we have chosen the case of a Ti sapphire laser operated at coi = 1.55 eV, i.e. a>i = 0.057 a.u., which is representative of the recently operated "femtosecond" sources. We have considered intensities li around lO l W/cm, which are typical. Note that, although such intensities are very high by laboratory standards, they remain quite moderate when compared to the "atomic" intensity, Iq = 3.5 lOl W/cm, which is associated to the field strength experienced by an electron on the first Bohr orbit in hydrogen, namely Fq = 5.1 10 V/cm. At intensities li =10 W/cm the atom can experience multiphoton ionization and even ATI, as shown in Fig, 1, which displays the simulation of a photoelectron spectrum for a peak intensity 1l = 2. 10 W/crri. Here, the pulse shape is assumed to be trapezoidal with linear tum-on and turn-off durations of one laser period Ti = 110 a.u., i.e. Ti = 2.6 fs), the total duration of the pulse being 8Tl. 

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