Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

Abstract

The NH(a(1)Δ) + CO(X(1)Σ(+)) product channel for the photodissociation of HNCO at 201 nm was investigated using the sliced velocity map ion imaging technique with the detection of NH(a(1)Δ) products via (2 + 1) resonance enhanced multiphoton ionization (REMPI). Images were measured for the NH(a(1)Δ) rotational states in the ground and vibrational excited states (v = 0 and 1). Correlation between the NH(a(1)Δ) and CO rovibrational state distributions were determined from these images. Experimental results show that the vibrational distribution of the CO fragment in the NH(a(1)Δ) + CO(X(1)Σ(+)) channel peaks at v = 1. The negative anisotropy parameter measured for the NH(a(1)Δ) (v = 0 and 1|j) products indicates a direct dissociation process for the N-C bond cleavage in the S1 state. A bimodal CO rotational distribution was observed, suggesting that HNCO dissociates in the S1 state in two distinctive pathways.

Imaging Isocyanic Acid Photodissociation at 193 nm: the NH(a1Δ)+CO(X1Σ+) Channel

“…Clearly, all the CO products display anisotropic angular distributions, and the values for the low-j and high-j components are only slightly different. This result is similar to our previous results [29]. It implies that both low-j and high-j components are from HNCO rapid dissociation via a repulsive surface on S 1 .…”

“…However, the anisotropy parameter β becomes considerably smaller as 1 NH rotational level increases. This phenomenon has been also seen previously in HNCO photodissociation at 210 and 201 nm [27,29], which could be explained by a non-axial recoil impact model [33]. As shown in FIG.…”

“…The photodissociation experiments were carried out on a time-sliced velocity map ion imaging apparatus described elsewhere [29,30]. In brief, a skimmed molecular beam containing 2% HNCO seeded in He was produced by a pulsed valve (General valve series 9) with a 0.5 mm nozzle.…”

Threshold photoelectron spectroscopy of unstable N-containing compounds: Resolution of ΔK subbands in HNCO+ and vibrational resolution in NCO+

“…Infrared (IR) and microwave spectra have been recorded, 11,12 and a number of experiments were aimed at photodissociation processes. [13][14][15][16][17][18] Photoionization of isocyanic acid was first investigated by Eland using conventional He(I) photoelectron spectroscopy (PES). 19 He determined the ionization energy (IE) for the formally non-bonding out of plane a ′′ (π nb ) molecular orbital to be 11.60 ± 0.01 eV and observed three 11.76 ± 0.01 eV.…”

Structure and IR Spectroscopic Properties of HNCO Complexes with SO2 Isolated in Solid Argon

“…Isocyanic acid (HNCO) is an intriguing molecule that has been widely studied both experimentally and theoretically [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. It is one of the simplest molecules containing all four important biogenic elements (C, N, O, and H).…”